Nghiên cứu quan hệ giữa tính chất và cấu trúc dãy anpha beta xeton không no chứa dị vòng thiophen bằng phương pháp tính gần đúng lượng tử

Va mat loan hoc, viec giai chinh xac phirong trinh Schroedinger ddi vdi cac he nay la rat khd khan, do dd cac nha khoa hoc da nghien ciiu va lian luc dua ra nhung luan cu ciia cac phiron

BO GIAO DUG VA DAO TAO DAI HOC QUOC GIA H A N O I TRirdNG DAI HOC KHOA HOC lUNHIEN

Le Thai Binh

NGHIEN COU QUAN HE GICA TINH CHAT VA CAU TRUC DAY

a,p - XETON KHONG NO CHLfA Dl VONG THIOPHEN BANG

PHl/ONG PHAP TINH GAN O O N G Ll/ONG TLf

LUAN AN THAC SI KHOA HOC HOA HOC

Chuyen nganh : Hoa Ly

LOl CAM ON Vdi Idng hiet ari sdu sac toi xin chdn didnh cam

an su huang dan tan tinh, day trdch nhieni cua thdy gido huang dan PGS TS Lam Nggc Thiem

Toi Cling xin chdn thdnh cam an cdc thdy c6 gido trong Khoa Hod, to ho mdn Hod ly cung todn the ban be gia dinh da dong vien khuyen khich, tao dieu kien vd giup da toi hoan thdnh ban hum an nay

Hd ngi thdng 6 nam 2000

Le Thai Binh

MUG LUC

Trang

Md dau 1 Chuong 1 : TONG QUAN 3

1.1 Sir phat trian va ly thuyet cac phuomg phap tinh gan dung trong hoa 3

hoc lugng tir

1.2 Cac quan diam nham giai gan diing phuong tnnh Schroedinger 6

1.2.1 Phuong trinh Schroedinger va phep gan diing Bom - Oppenheimer 6

1.2.2 Ly thuyet trudng tir hop Hartree Fock ( Harlree Fock SCF ) 8

1.2.3 Phuong irinh Roolhaan 11

1.3 Cac phuong phap giai gan dung 13

1.3.1 Phirong phap AB initio hay phuong phap linh khong kinh nghiem 14

1.3.2 Cac phirong phap ban kinh nghiem 14

1.3.2.1 Phuong phap gan diing Huckel ( HMO) 15

1.3.2.2 Phirong phapCNDO ( Complete Neglect of Differential Overlap ) 16

1.3.2.3 Phuong phap INDO ( Intermedate Neglect of Differential Overlap ) 17

1.3.2.4 Phuong phap MINDO ( Modified Intermediate Neglect of Diatomic 18

Overlap )

1.3.2.5 Phirong phap MNDO (Modified Neglect of Diatomic Overlap ) 19

1.3.2.6 Phuomg phap AMI ( Austin's Model 1) 20

1.3.2.7 Phirong phap PM3 ( Parametric Model 3 ) 20

1.3.2.8 Phirong phap ZINDO/S ( Zemer\s INDO ) 20

1.4 Doi tirgng nghian ciru ciia da lai 23

1.4.1 Dae diam \e cau iriic ciia hop chat khao sat X- C i R p S 24

1.4.1.1 Nhan phenyl va vi iri the para 24

1.4.1.2 Nhan ihiophen 26

1.4.1.3 Nhom carbonyl va sir dich chuyen electron trong mach 27

Chircmg 2 : PHAN THUC NGHIEM VA BIEN LUAN KET QUA 30

2.1 Phrin mem \'a cac biroc lien hanh nghien ciru 30

2.2 Cac birdc lien hanh khao sat 32

2.3 Lua chon phuong phap 33

Trans 2.4 Phat trian mach 35

2.5 Anh huong cua nhom the para - phen\'l ihuoc phan tir A4X \a B2X 45

2.5.1 Anh huong cua nhom the Ian nang lugng loan phan nang luong lien 47

ket, nhiet hinh thanh

2.5.2 Anh huong cua nhom the len gia tri momen Iiroiig cue 49

2.5.3 Anh hucmg cua nhom the lan dien tich cua nguyan tir Oxy ^^

2.5.4 Anh huong ciia nhom the Ian dien ifch cua nguyan tir S va di vong

ihiophen

2.5.5 Anh huong cua nhom the den dao dong ciia phan tir 58

Chuong 3 : KET LUAN CHUNG 61

Tai lieu iham khao 63

Phu luc 66

MOOAU

Ngay nay phuong phap hoa hoc luong lir da dugc ap dung vao hau het cac 17nh vuc cua hoa hoc va da dal dugc nhung thanh lu dang ka Sau gan 30 nam iha nghiem vdi bao bude thang tram, cuoi cung thuc lian da xac nhan phirong phap hoa hoc lugng lu da Iro thanh phuong phap khong the thieu dugc trong nghien ciru hoa hoc hien dai PhSn ihudng Nobel nam 1998 ve hoa hoc tang cho giao su J Pople - cha de cua cac phuong phap tinh gan diing hoa lugng tu - la mot minh chung cho nhung nhan xet nay

Dua vao ket qua tinh cua cac phuong phap gan diing ngudi la da xac dinh kha chfnh xac cac tinh chat lugng tu nhu mat do electron, dien ifch hieu dung trcn tung nguyen tu, bac lian ket, chi so hoa tri tu do Cac Ifnh chat vT mo ciia phan tu nhu cau triic, the ion hoa , nhiet hinh thanh, momen luong cue, tan so quang pho Cung bang phuong phap nay cac dai lugng nhu do dai lien ket gdc van, gdc nhi dien da dugc xac dinh luong ddi chinh xac so vdi cac gia tri do dugc bang thuc nghiem

Co the ndi phuong phap hoa hoc lugng lir khong phai la mo hinh trang trf hoac nhung phae thao via'n vong tren giay nhu ngudi ta ludng trudc day ma no da thuc sir tro thanh cdng cu huu hieu khong tha ihay the trong nghian cuu hoa hoc

Ap dung cac phirong phap lugng tu trong ban luan van nay chung toi can giai quyet cac van de chinh sau day :

I Tien hanh xac dinh cac tinh chat lugng tu va cau triic cho mot so dSn xufU cua a,p - xelon khong no chua di vong ihiophen Nhung hgp chat nay trong ihirc lian cd hoat ti'nh sinh hoc cao nhu kha nang khang the Idn chong cac virus

va cac lac nhan gay ung ihu Chiing cung la cac thude ihir huu co dung trong phan

tfch cd do chon Igc do nhay cao va la nhung san pham irung gian cho nhieu qua trinh tdng hgp huu co quan trong

2 Tran co so nhung so lieu ihu dugc chiing toi se xem xet mdi luong quan giua cau tnic va tinh chat cua phan tir nhu qui luat phan bd electron trong phan tu anh huong cua cac nhdm the den qui luat nay, cau dang uu lian va kha nang phan ung

Mat khae, cung tu nhiJng ka'l qua tinh loan, chiing toi se so sanh vdi cac so lieu thuc nghiem ihu dugc bang cac phuong phap hoa ly khae nhau de' nil ra cac

nhan xet can thiet \t cau true va co che phan Ung

CHirONG 1 -TONG QUAN

1.1- Sir phat trien ve ly thuyet cac phuong phap tinh gan diing trong hoa hoc lugng tu

Hoa hoc lugng tu cd the coi la sir ap dung co hoc luong tu vao hoa hoc nham giai quya't va mat ly thuyet cau triic quan he giua tinh chat hoa hoc \'a cau triic cua cac nguyan tu va phan tu Tran quan diem ciia hoa hoc lugng tu mot ddi lugng khao sat ( nguyan tu, phan tu, ion, gdc tu do v.v ) dugc xac lap neu nhu xac

dinh dugc ham sdng \\J va nang lugng E cua he cung nhu cac dai lugng lugng tu,

cac thong so cau tnic va cac tinh chat hoa ly khae

Theo hoa hoc lugng tu, sir bien ddi trang thai cua he vat ly vi mo dugc biau dian bang phirong trinh sdng Schroedinger 6 trang thai dung | 9 | :

Hi/^{q)=E{q)

E - nang lugng

v[/(q) - Ham sdng

q la yen to toa do

// - loan tu Halminlon ciia he ,

II = T -¥]' { V - the nang cua he, T - dong nang cua he )

Cac nghiem cua phuong trinh tren cho ta biet cac ham sdng mo la trang thai ciia he, va nang lugng luong ung Nhu vay viec giai dugc phuong trinh tran

dong nghla xai viec xac dinh dugc he Thdng thudng ddi tugng khao sat ciia ha la

: nguyen tu ( he nhiau hat mot tam ), he phan tir ( nhiau hat, nhieu lam) Va mat loan hoc, viec giai chinh xac phirong trinh Schroedinger ddi vdi cac he nay la rat khd khan, do dd cac nha khoa hoc da nghien ciiu va lian luc dua ra nhung luan cu ciia cac phirong phap gan diing nham don gian hoa chuyen phuong trinh Shroedinger phi'rc lap thanh dang cd the giai dugc

Tu phuong trinh Iran loan tu H c6 dang

H = t e + t n + Uee + Uen + Unn Trong dd :

f e - dong nang cua electron

j ^ - dong nang cua hat nhan

U^^- the nang luong lac giua cac electron \di nhau

(] ^n - the nang tuong tac giua cac hat nhan va cac electron

{j „^ - the nang tuong tac giua cac hat nhan vdi nhau

Mot each Idng quat, gia sir mot phan tu cd N hat nhan va n electron

Do khoi lugng nguyan tu tap trung o hat nhan nan, mot each gan diing, coi hat nhan cd dinh Vay H trong phirong trinh Schrodinger chi bao gdm ba thanh phan ;

H = Te + Uen + Uee Dfiu lien de de giai phuong trinh sdng Born - Oppenheimer chi quan lam den dong nang cua electron t e va the nang tuong lac electron - hat nhan fj,,,, liic nay loan tu Halminton cd dang :

H* = t e + Uen Day la gan diing bac khong

Tiep theo khi khao sal he nguyan tu nhieu electron Harlree da trung binh hoa thanh phan L\.^>, coi electron chuyan dong trong mot irudng trung binh tao

bdi cac electron khae trong he ham sdng \\f dugc xac dinh nhd phuong phap

IrUcYiig tu hgp SCF Fock tiep tiic dua them ham orbital - spin bieu dien ham sdng dudi dang dinh thuc Slater nhd dd ham sdng lim dugc theo Hartree Ird nan phan ddi xung phu hgp \'di nguyen ly Pauli Cac ket qua tinh loan theo phuong phap na> kha phu hop \'di cac ket qua thuc nghiem Den nay, phuong phap gan diing Hartree - Fock dugc coi la phuong phap kha hoan chinh de khao sal nguyen tu

Dd'i vdi ha phan tu, so vdi quan diam cua Hartree Fock, he con cd tham cac luong tac giua cac hat nhan khae nhau vdi electron Do dd la khong tha ap dung phuong phap Hartree Fock de giai quyet dugc van da nay Roolhaan da da nghi mot phuong phap mang tan dng Ham sdng phan tu MO dugc mo la nhu Id hgp luyen tinh cua cac ham sdng co so MO-LCAO ( cac ham sdng co so dugc goi la tap ham co so ) Bang phuong phap irudng tu hgp - SCF Roolhaan tim dugc he nghiem cac ham sdng md la he nhiau hat trong phan tu, ham sdng nay cd dang la

Id hgp luyen tfnh cac ham co so vdi cac he so thich hgp Cho den nay phuong trinh

do Roolhaan dua ra la co so cho cac phuong phap tinh gan diing sau nay

Den nay cd ba huong phuong phap da giai gan diing phuong trinh Roolhaan

DAu ticn la phirong phap ihuan tuy loan hoc AB-initio | 12|, trong phucrng phap nay, ngudi la sir dung cac phuong phap gan diing loan hoc nham don gian hoa qua trinh giai Phuong phap nay nhin chung ddi hoi linh loan kha phi'rc tap nc'u so vdi hai phuong phap sau, nhung mat khae cd tha ap dung cho hau het cac dang phan tir

Phuong phap ihu hai dua vao cac quan diam ve can hinh hoa hoc de don gian hoa qua trinh giai bang each giam so ham co so xay dung nan orbital phan tu 114]

Trong phirong phap ihu ba da don gian hoa, cac nha khoa hoc dua vao cac tham so hoa ly thu dugc nhu nhiet tao thanh, moment ludng cue, the ion hoa, ai luv vdi electron do am dien va cac ket qua phan tfch cau tnic ma tien hanh tham

sd hoa cac thanh phan ciia phuong trinh Roothaan trong qua trinh giai Chiing la se xem xet chiing mot each cu the trong cac phan tiep theo

1.2- Cac quan diem nh^m giai gan diing phuong trinh Schroedinger •

Nhu da biet, phuong trinh Schroedinger trong cac he nhieu hat ndi chung la

ra'l phiic lap, khong tha giai dugc chinh xac Do dd cac nha khoa hoc ludn lim cac

phep gan diing nham don gian phuong trinh, bien chiing cd tha giai dugc Theo

mirc do phiic tap cac phep dd la : phep gan diing Born - Oppenheimer, Hatree Fock

va Roothaan

1.2.1 - Phuong trinh Schroedinger va phep gan diing Born - Oppenheimer

Co hoc lugng tu da giai thich dugc tfnh chat ludng tinh sdng - hat cua cac

hat vi md, phuong trinh Schroedinger la phirong trinh sdng md ta he cac hat vi md

Phuong trinh cd dang l6ng quat;

H\\f{q)=Ex\}{q) ( 1 0 1 )

Trong dd \|/ la ham sdng md ta he chi phu thude vao toa do cac hat trong he ( c/)

ggi la ham sdng d trang thai dung, tich ciia i(/ va lien hctp phirc ciia nd \|/* cho la

bici xac suai bat gap hat, E la nang lugng , H la loan lii Hamilton bao gdm hai

thanh phan dong nang va the nang cua he :

-H = t + V (1.02) Trong dd

T : Toan tu dong nang cd dang T = h' V'/ 87i'm (1 03)

Vdi h : hang sd Planck, V^ : toan tu Laplace, m : khoi lugng hat

V ; Toan lii the nang cd dang V = -q,qV r

Ta cd tha thu dugc nang lugng cua he va cac tinh chat lien quan nhd giai

phir(mg trinh Schroedinger Nghiem ciia phuong trinh la cac ham sdng \|/ va nang

lucyiig E luong ung vdi cac trang thai khae nhau ciia ha

Phuong trinh (1.01) edn cd tan goi la phuong trinh Schroedinger khong phu

thuoe thdi gian Chii y rang phuong trinh nay khdng md ta diing cac he trong do

toe do chuyan dong ciia cac hat gan bang toe do anh sang ( \i du nhu he cac

electron Idi chuyan dong gan cac hat nhan Ion )

Doi vdi he bao gdm cac hat nhan va electron loan tu H trong phuong trinh

M,, Z, la khoi lugng va dien tich cua hat nhan i

m la khoi lugng cua electron

e la gia tri dien tfch ciia electron

r ,, la khoang each giua hai hat i va j bai ky (i,j cd tha la A,B,p, q v.v )

A,B, p, q la cac chi so da phan biet cac hat nhan va cac electron riang biet

Theo quan diam ciia Born - Oppenheimer, bofi vi cac hat nhan cd khoi lugng

Idn gap hang nghln Ian electron do dd la cd the coi gan diing hat nhan gan nhu

dirng yan so vdi electron ( T „ = 0 ) va khi dd U,,„ la hang sd Ndi each khae Born

-Oppenheimer coi electron chuyen dong trong mot Irudng do cac hat nhan d trang

thai tinh, {\x do suy ra tuong lac giija electron vdi hat nhan va phfa hat nhan chi

phu ihuoc vao toa do ciia hat nhan ma khdng phu ihuoc vao idc do ciia hat nhan

Nhu vay Boni - Oppenheimer da tach H trong phuong trinh (1.05) ra de thu

dugc loan tii J[ lien quan den electron :

!H = - - 4 M ; v=-xi;.^z,.;>x.v-/ (1.06)

OTT m J A p p<q

Trong ly thuyet orbital phan tu chiing ta thudng chi quan tam den cac ham

sdng cua cac electron , do dd thudng chi sir dung toan tu ^{^ hay vi sir dung loan tu

H Phuong trinh Schroedinger sau khi da dugc Born - Oppenheimer sua ddi cd

dang :

Jt \\f(q) = E\\f(q) (1.07)

Do chenh nang lugng £ thu dugc do giai phuong trinh (1.07) va E do giai phuong

trinh (1.01) la phan the nang tuong tac day giiJa cac hat nhan :

E = ' £ + ^e-Z^,Z^r AB 1

A<fi

Nhu vay Born - Oppneheimer da don gian lam cho toan tir H trong phirong

trinh Schroedinger ban dfiu chi con ha thanh phfin lien quan den dong nang ciia

electron , the nang tuong tac giiia electron va hat nhan dugc coi la dung yan, va

the nang tuong lac giua cac electron vdi nhau Vdi phep gAn diing nay , phucrng

Irinh Schroedinger da don gian di nhung van edn phiic tap khi giai nhat la thanh

phan cudi ciing trong phuong trinh (1.06) - the nang luong lac giua cac electron

vdi nhau Hartree Fock da tiep luc giai quyet van de nay

1.2.2 Ly ihuvet irudng tu hop Harlree Fock ( Hartree Fock SCF )

Trong ba thanh phan ciia phirong trinh ( 1.06) Hartree phan biet : hai thanh

phan dau chi lien quan den mot electron khi dd phuong trinh (1.06) cd dang :

// = / / ' X Z e'r-; (1.08)

n

Harlree coi ham sdng ciia he \|/ = ]~[ (// ' (1.09)

Tich na> goi la tfch Hartree, trong do V|; va ^i, la nghiem cua cac phuong trinh

Hv|; = Ev|/ va H, M/, = E , V|/,

Dd'i vdi he nguyan tu bao gdm mot hat nhan \ a n electron H = Z^H

Di dua toan tu cho boi phuong trinh (1.08) chi lian quan den toa do cua

mot electron Hartree da lay trung binh :

Dd'i vdi he nguyan tir, nghTa la sir phan bo electron quanh hat nhan cd dang

hinh can, the nang cua electron chi phu thude vao khoang each cua nd vdi hat

nhan , moment gdc la hang sd khi dd la cd the' giai dugc phirong trinh (1.10) neu

cd mot ham i|/ cho Irirdc Dd la phep gan diing do Harlree Fock de nghi

Mudn tfnh dugc tfch phan J ,j trong phuong trinh ( 1.12) can mot ham sdng

da xac dinh the nang tuong tac trung binh giua cac electron vdi nhau de roi cudi

Cling giai phuong trinh Schroedinger lim ra ham sdng NghTa la phuong trinh chi

tim dugc nghiem khi da biet dugc nghiem Da giai quyet van da nay Harlree da de

nghi phuttng phap irudng tu hgp SCF ( Self Consistent Field ) Theo phuong phap

nay trong qua liinh tfnh loan ban dau la phai gia dinh da tim dugc ham sdng \(/\

Xiic dinh J,j ddi \di ham i|/" sau dd lim ra ham i[;' lap lai qua trinh cho dcii khi v(/'''

=t i(/' Qua trinh dugc coi la hoi lu va ham sdng \i/' dugc coi la nghiem ihfch hgp

cua phirong irinh Schroedinger Phirong phap nay da dugc Roolhaan sir dung de

giai phirong trinh Schroedinger dd'i vdi he phan lii

Tuy nhian ham sdng \\f tim dugc tiJ phuong trinh (1.09 ) la ham ddi xihig

ngugc vdi nguyan ly Pauli Fock da cai tien til ham sdng Harlree liic na\' ham v|/

cd dang:

\\) = I// <j (1.13)

Trong dd:

a la ham spin

^ l a ham sdng trong phuong trinh cua Harlree

Vdi ham sdng orbital spin nayham sdng ciia he dugc Fock td hgp dudi

dang:

i|/=(N!)-'^^|^,(T/y)| (1.14)

C) day \y/,a^(jy la dinh thuc Slater, N la Idng sd electron trong he Viec chuyen vj

hai electron lUcyng duong vdi viec hoan ddi vi trf hai col ciia dinh thuc dan den ddi

da'u Vdi hieu chinh ciia Fock, ham sdng tim dugc la ham phan ddi xirng phu hgp

vdi nguyen ly Pauli

Fock edn cd mot ddng gdp quan trong trong viec trung binh hoa the tuong

tac giiia cac electron vdi nhau [29] Ham sdng Hartree dugc td hgp dudi dang

N

tfch Harlree, nghTa la ^'1 = YW^^' • ^^^ ^^ thuyet vi xac suat cd nghTa la Hartree

coi die electron chuyen dong doc lap ddi vdi chuyen dong cua cac electron khae

Khi tfnh loan the tuong tac trung binh electron - electron Hartree chi chii y den

tfch phan Culdng J,, Dieu nay cd nghTa Hartree chi chii y den tuong tac tTnh dien

irirc liep giua cac electron / / ma khdng quan lam den anh huong cua Irudng do

cac electron edn lai Trong phirong phap Fock, nang lugng ciia he theo cai lien

ciia Fock la :

^ = Z^"' + ZZ-^""^-ZX^'.^> (1-15)

Trong dd :

E^ - nang lugng bao gom ddng nang electron va the nang do tuong tac hiit

giiia hat nhan va cac electron

Jn,n la tfch phan Culdng dac trung cho tuong tac day giua hai electron chiem

hai orbital m va n :

Krnn 1^ tfch phan trao ddi tfnh vdi Irudng hgp hai electron i va j

•>

K^„ = J K ( ' k ( ' ) f V^.OkO>/r,^r^ (1.17)

Nhu vay Fock da dua vao trong the trung binh thanh phan K^in dac trung

cho tuong tac trao ddi giiia cac electron Phuong phap Hartree Fock dugc coi la

phuong phap kha hoan chinh de giai cac bai loan nguyen tii [30j

1.2.3 Phucrng irinh Roolhaan

Nhu da biet phuong phap Hartree Fock khdng the ap dung ddi vdi he nghien

cuu la Ccic phan tu De giai quyet van da nay, Roolhaan da dua ra phirong phap cua

minh Phirong phap Roolhaan sii dung phuong phap bien phan , chon cac ham

Ihich hgp la td hgp tuyen tfnh ciia cac ham (t),, cac ham (j), lap thanh bo ham co sd

da bieu dian cac orbital va diau chinh cac thdng so ciia nd de chuyan chiing vi

dang gan vdi cac orbital Hartree Fock Dd la quan diem cua phuong phap

Roolhaan

Thdng ihudiig ngudi ta sir dung ba bo ham co sd nhu sau :

Cac bo ham co sd toi ihia'u ; bao gdm cac AO , cac orbital ciia Idp vd hoa

Iri cua mdi nguyan lii trong phan tu

Cac bd ham ca sd mo rgng : nhu cac bo ham co so toi thieu cd tfnh them

vao cac AO nam ngoai Idp hoa tri ciia mdi nguyan lii

Bo ham co sd hoa tri : Chi bao gdm cac orbital ciia Idp hoa iri ciia mdi

ngu\'en tu

Ham sdng phan lir ihco Roothaan cd dang :

Con cac orbital cua Hartree Fock la nghiem cua phuong trinh :

Viec di6u chinh cac he so 3,^, de ham song v|/ co dang gan giong \6'\

orbital Hartree Fock dong nghTa voi gia tri E^ dat circ tieu, trong do E^, :

d day F,j la thanh phan cua ma tran Fock va dugc xac dinh : F^^ = {(p^Ttp^d^

Sjj - la tfch phan xen phii

Di giai ham sdng nay, Roothaan sii dung phuong phap tu hgp cua Hartree

Fock

Tii bo ham co sof (j)/, Roolhaan giai lap mot ham sdng MO y/^ tuong ling vdi cap

cac he sd a^ :

^ > Z O ' (1.23)

Sir dung ham \|/" de' xac dinh toan tir Hartree Fock tirong ijng H ' r6i sir dung giai

cac phuitng trinh (1.12 ) va ( 1.14) de tim ra mot bo cac orbital dugc mo ta bai

V/', va bo cac he so tuong ung a\^ Lap lai qua trinh cho den khi cac ham song

phan tu va bo cac he so hoi tu khi do thu dugc Idi giai

Nang luong cua mot electron lai MO \i thu dugc cd dang tuong tu Hartree

Fock

^ = ^ ^ 1(2^ - ^.J (1.24

Trong do e^ dai dien cho ddng nang ciia mot electron tai MO |.i \'a the tuong tac

hiit gay ra bdi cac hat nhan ( thdng ihudng ggi la nang lugng tuong tac Idi ),

y]{2J^ - K^ ) la gia tri trung binh the nang luong tac cua electron lai MO |i

vdi cac electron khae trong phan tii Trong qua trinh tfnh loan theo phuong phap

Irudng tu hgp SCF, y/^ la MO dau tian ma Roothaan giai lap da tfnh loan

J,^^ dac trung cho tuong tac day trung binh ciia electron dang chiem MO i//^^ va

mot electron dang chiem MO ^//," , theo Roothaan nd cd dang cu the

dd la qua trinh giai gan diing cac phuong trinh chiia cac tfch phan Culdng va cac tfch phan xen phu giua cac electron

1.3 - Cac phirong phap giai gan dung :

Cac phir(Tug phap giai gan diing phirong trinh Roothaan dugc hici hien nay bao gdm cac phinmg phap linh gan diing loan hoc AB- mitio cac phucrng phap

giam sd ham co so Mulliken va cac phuong phap ban kinh nghiem sir dung cac tham so thuc nghiem: CNDO NDDO INDO AMI PM3 MINDO ZINDO

1.3T - Phuong phap AB -initio hay phuong phap tfnh khdng kinh nghiem :

Phuong phap AB initio khae vdi cac phuong phap ban kinh nghiem o cho la trong qua trinh tfnh loan khdng sir dung cac tham sd tii thuc nghiem [221 Thay vao

dd qua trinh tfnh loan chi sir dung cac qui luat cua co hgc lugng tu va mot vai hang

s6 vat ly [ 19 ] bao gom :

- Toe do anh sang trong chan khdng

- Dien tfch va khoi lugng ciia electron va hat nhan

- Hang sd Planck

Phirong phap AB-initio dua vao cac phep gan diing loan hgc o mire nghiem ngal 120] Sir khae nhau giua phuong phap ban kinh nghiem va phucrug phap AB-initio la sir phiic tap trong tfnh loan va do chfnh xac ciia ket qua Phirong phap AB-initio cd mot Idi giai kha chfnh xac cho hfiu het cac he phan tii Cung cd the ndi phirctng phap AB-initio la sir tfnh ti^r dau cho tat ca cac tfch phan bang phep giai tfch 121] Mac dii phirong phap AB-initio cd do tin cay va chfnh xac cao nhung nd cung cd Ccic han che nhu can bo nhd Ion, idc do tfnh cao, thdi gian linh loan lau hon nhieu lan so vdi phirong phap ban kinh nghiem

1.3.2 - Ccic phUQ-ne phap ban kinh nghiem :

Xuat phat lir tfnh thuc lian trong tfnh loan, sir giam bdt chi phf thdi gian linh va ka'l qua thu dugc van nam trong pham vi cho phep da xet doan cac qua Irinh hoa hgc ma la tim kicm cac phuong phap mdi Cac phirong phap ban kinh

nghiem xuai hien di dap ung nhu cau nay Nhung phuong phap ban kinh nghiem

da sii dung cac iham sd thuc nghiem thay the vice tfnh cac tich phan phiic lap don

thuan ly thuyet Nhd sir loai bo hang loat cac tfch phan, cac phuoiig phap gan dung

ban kinh nghiem lan lugt ra ddi Ta xet mot sd cac phuong phclp sau :

1.32.1 Phirang phap gan diing Huckel ( HMO)

Ngay tii nam 1931, can cii vao cac tfnh chat hoa hgc dac trung cho he

phan tu huu co lian hgp n , Huckel da da xudng phuong phap HMO ( Huckel's

Molecular Orbital) Phuong phap nay ra ddi da gdp phan dinh lugng hoa cac dai

lugng nhu mat do electron q,, bac lien ket p^, , chi sd hoa tri tu do F, di xet

doan CO che cung nhu cau dang ciia mot sd hgp chai huu co he lian hgp

MO - Huckel la phuong phap td hgp luyen tfnh cac AO nhung chi ap dung

dd'i vdi Ccic electron n Bang vice ap dung phuong phap bien phan, xac dinh gia tri

ruing lugng va ham sdng ciia he electron TI qui vi giai he cac phuong trinh :

\H„-S„E\ = 0 (1.27)

trong dd, vc irai dugc ggi la dinh Ihiic the ky

H va S la cac ifch phan Huckel da de xuat each xap xi trung binh nhu sau :

Neu i=j thi H,j = a ggi la tfch phan Coulomb

Neu i;^j thi H,, = [3 ggi la tfch phan trao ddi

Cac Irudng hgp edn lai : H,j = 0

Tuctug tu nhu vay, ddi vdi tfch phan xen phii S ta cd :

Na'ui=jlhi S,j=l (1.28) Neu i^j thi S = 0

Trong cac Irudng hgp lian hgp va siau lian hgp cd chiia cac di to cac gia tri

ciia a \ a [i hi thay ddi vdi cac gia tri tfnh ti^r cac he khdng chira di to mot he sd (

thdng thudng cac he sd dugc xac dinh bang thuc nghiem ddi vdi tung he cu the ):

a, =a, + / ' , A

Tuy nhien phuong phap HMO da bo qua tuong tcac day ciia cac electron a

nan pham vi ung dung chua dugc mo rgng Da khc^c phuc dieu na\ Hoffman da

phat trien HMO thanh phuong phap Huckel mo rgng ( Extended HMO ) Trong

phuong phap nay ngudi ta da tien hanh tfnh cac tfch phan xen phii S,, thay cho viec

gan cho nd nhung gia tri tuy y Phuong phap MO- Hucken mo rgng diing da tfnh

loan nang lugng, khdng diing de td'i uu hoa hinh hgc hay tfnh loan cac thdng sd

nhiet ddng phan tii Ket qua cua phuong phap nay cho ta mot sir md ta cac orbital

phan tu d muc dinh tfnh va ban dinh lugng, cac tfnh chat nhu dien tfch dinh cU va

sir phan bd spin Vdi phuong phap nay ket qua tfnh da kha di ho*n nhung van dung

d muc gan diing ihd

1.3.2.2 Phuangphdp CNDO { Complete Neglect of Differential Overlap )

Tan cua phuong phap cd nghTa la bo qua hoan toan cac vi phan phu ciia cac

electron thude cac nguyan tu khae nhau Day la phuong phap ban kinh nghiem

don gian nhat tfnh loan theo phirong phap Irudng tu hgp Nd dugc diing da tfnh

loan die tfnh chai ciia electron d trang thai co ban, ddi vdi ca he vd md v;i he vd

ddng, toi uu hoa hinh hgc va Idng nang lugng Trong phuong phap CNDO, chi xet

den cac electron hoa tri , Idp vd tro dugc coi la mot phan cua Idp Idi, va gdp tuong

Uic day cua lop nay vao tuong tac cua hat nhan vdi electron

Nhu da biai trong phuong phap Irudng tu hgp qua mdi qua trinh tfnh loan

ngudi la deu sir dung gia tri nang lugng nhu la mot tiau chi de danh gia sir hoi tu

qua dd tim dugc ham sdng luong ung vdi mot bd ham co sd cu the.Theo phuong

phap bicii phan va bang each bien ddi loan hgc ta thu dugc nang lugng electron

Ppv la cac yen Id ma Iran mat do

/iuUcr) 1^'* ^^^^^ \>lr^\\ the hien tuong tac giiia hai electron cd dang :

Phuong phap CNDO don gian hoa phuong trinh Roolhaan bang each xu ly

2 Bo qua tfch phan xen phu trong tat cac cac tfch phcan cd hai electron

{lJv\?La) = {pv\Xa)5^^^5^_^ trong dd 6 la cac delta Kronecker

3.Trung binh hoa cac tfch phan Culdng ddi vdi mdi cap electron

{po\Xa) = ?i.^f, {(p^, Iran A va (p, tren B)

4 Bo qua xen phii don phan tii trong cac tfch phan trao ddi vdi Idi ciia cac nguyan tu khae

5 Coi cac yen td ma tran cheo Idi lian quan den hai nguyan tu ty le vdi cac tfch phan xen phii tuong ung

Nang lugng electron tdng cdng ciia phirong trinh Roothaan qua cac phep gan diing cd tha coi la tdng ciia hai thanh phan : thanh phan lien quan den mot electron E, va thanh phan lian quan den cap electron E^R

Cung vdi sir phat trian, sir tham so hoa trong phuong phap CNDO cho ra ddi Ciic phien ban CNDO/1, CNDO/2 Trong hai phuong phap nay, phian ban CNDO/2 cd quan diem rat gan vdi phuong phap sau la phirong phap INDO

1.32.3 - Phirang phap INDO ( Intermediate Neglect of Differential Overlap )

, 3

Phuong phap nay la phuong phap ban kinh nghiem do Pople Beveridge va

Dobosh dua ra Trong tfnh toan, phuong phap gian tiep bo qua cac vi phan phii

Nhu vay nd uu viet hon phuong phap CNDO a chd cd tfnh den cac lire day bat ky

giia cac electron tren ciing mot nguyan tu Phuong phap na\ dugc ap dung de tfnh

loan cac tfnh chat cua electron trong cac he vd ddng va vd mo, tdi uu hoa hinh

hgc va nang lugng tdng cdng

Nhu ta da biet, theo quan diam phuong phap CNDO khdng phan biet tuong

lac giiia hai electron cd spin song song hoac ddi song, dac biet khi chiing ciing

nam trong mot nguyan tu Do tfnh phan doi xiing ciia ham sdng, cac electron cd

spin song song khdng the chiem cung mot d, va do dd hai electron 6 hai AO trong

cung mot nguyan tu se cd the nang tuong tac day trung binh nho hon neu chiing

cd spin song song Va mat loan hgc, diem khae nhau na\ dugc coi nhu xet lich

phan trao doi hai electron cd dang :

(/vu|H= JK0K(2)-^, OM (2) (^^^) n.32)

' 1 2

Trudng hgp la xet 0 day O^, Ou cung thugc mot nguyan tu Phuong phap

CNDO bo qua cac tfch phan cd dang nay | 2 4 | va thay tai ca cac tfch phan giua

hai electron tran ciing mot nguyan tir bang y ma khdng ka den spin ciia chiing Do

dd Ccic ka'l qua tfnh loan theo phirong phap CNDO khdng cho la biet sir tach trang

thai Ngoai ra, do qua trinh trung binh hoa sir tuong tac xen phii ciia hai electron

Iran Cling mot nguyan tii, phuong phap nay khdng tha giai quyet dugc van da tach

trang thai trong cung mot cau hinh

PhucTug phcip INDO cd mot so sua ddi giii lai cac tfch phan xen phii don

nguyen tu nhung chi \di cac tfch phan cd dang mot tam Phirong phap nay thudng

dugc ggi la phuong phap gian tiep bo qua cac tfch phan xen phu

J.32.4 - Phirang phap MINDO ( Modified Intermediate Negelect of Differential

Overlap )

Phuong phap nay dugc xay dung dua vao viec sua ddi phuong phap INDO

do Dewar dua ra lan dau tian vao nam 1969 Qua trinh tfnh toan trong phirong phap nay la ap dung phuong phap trudng tu hgp Su sua ddi o day la phuong phap MINDO/3 diing cac tham sd phii hgp vdi thuc nghiem thay vi tap trung vao tfnh loan mdt each chfnh xac Phuong phap nay thfch hgp vdi cac ddi tugng la cac phan tii chai huu CO Idn, cac cation, cac hgp chat polynilro Cac ket qua linh loan da mang lai cac thdng tin can thiet ve tfnh chai electron , sir tdi im hoa hinh hgc va nang lugng loan phan

Cling mot CO sd ddi vdi phuong phdp MINDO cd cac cai lien, dd la cac phicn ban MlNDO/1, MINDO/2, MINDO/3|161 Phirong phap MINDO/1 lien hcinh tham sd hoa de tfnh cac tfch phan mot tam, tfch phan day hai tam va tfch phan tuong tac hiit giira hat nhan va electron MINDO/1 coi tfch phan cdng huong ciia mot electron la ham sd cua khoang each giua cac hat nhan Phuong phap MINDO/2 cai tien tham, coi tfch phan day Idi la ham so ciia khoang each giua Ccic hat nhan Phuong phap MINDO/3 la phirong phap trung gian giua cac phuong phcip CNDO, INDO ca NDDO ( Neglect of Diatomic Differential Overiap ) trong

dd chi bo qua vi phan phii hai orbital d hai nguyan tu khae nhau Phuong phap nay sir dung cac bg ham co sd Slater - Zener STO - 3G, 4 -31 G, 6- 31 G [ 14|

1.3.2.5 - Phirong phdp MNDO ( Modified Neglect of Diatomic Overlap )

Phuong phap MNDO la phirong phap MINDO da dugc hieu chinh, trong qua trinh tfnh toan six dung ihuat loan tu hgp Dai ap dung cua phirong phap nay

la Ccic phan lir hum co cd chiia cac nguyan to thugc chu ky mot va hai ciia bang he thdng tan hoan, loai trir cac kim loai chuyan tiep [15] Phuong phap nay dung da ifnh loan cac tinh chai electron va cac thdng sd hinh hgc cac phan tii da dugc tdi

uu nang luctug loan phan \'a nhiet hinh thanh

1.3.2.6-Phuangphdp AMI ( Austin Model 1 )

La phuong phap trudng tu hgp ban kinh nghiem dugc ap dung kha phd bien hian nay [17] Phuong phap nay la kai qua cua xiec cai tien phuong phap MNDO, ap dung cho cac nguyan tu thude chu ky mdt, hai va ba ciia bang he thdng tu^n hoan loai trii cac kim locai chuya'n tiep Cung vdi phuongphap PM3 phuong phap AMI nhin chung la phuong phap ban kinh nghiem chfnh xac nhat diing da tfnh loan cac tfnh chai electron [17J, tdi uu hoa hinh hgc, nang lugng toan phan va nhiet hinh thanh

1.3.2.7 - Phirang phdp PM3 ( Parametric model 3 )

Phirong phap PM3 cung ka mot phirong phap ban kinh nghiem sii dung ihual hKin Hi hgp Phirong phap PM3 la sir tham sd hoa mot lan nua ciia phU(rng phap AMI Qua trinh tham sd hoa trong PM3 dp dung cho nhieu nhdm nguyen td thugc nhdm chfnh, loai trii cac kim loai chuyan tiep [271

1.3.2.8 - Phirang phdp ZINDO (Zerner's INDO )

Day la phuong phap ban kinh nghiem dugc phat trien boi giao sU C Zcrner lai iruitug dai hgc Guelp, Ontario, Canada \'a trudng dai hgc tdng hgp Florida, Gainesville, Florida USA [33] Phirong phap ZINDO cai lien tu cac phirong phap Huckel md rgng, CNDO, INDO va PPP cho phep tfnh toan nang lugng, tuong tac cau hinh ( phd electron tii ngoai kha kien ) Phuong phap cd the ap dung cho hau hei Ciic kieu phan lii bao gom cac hgp chai sinh hgc, cac chai co kim cac chai huu

CO Trong tfnh loan, ZINDO sii dung ihual loan tu hgp [27] , qua trinh nay cung

md phong khao sal phan tii dudi dang bi solvat hoa trong trudng dien hoac cac dien iich diem ZINDO da tham sd hoa hon 30 nguyan id thugc chu ky mdt , hai va ba ciia bang he thdng luan hoan ke ca cac kim loai chuyan tiep Gidi han khao sal ddi

\di ZINDO thdng ihudng la cac phan tiVcd chua khoang 2?() nguvcn tu va khi dd

ZINDO su dung chiing 1000 ham co so Vdi cac phian bean Idn hon ZINDO cd tha

mo rgng gidi han ddi vdi phan tu gom 1000 nguyan tu thi hcam co sd dat tdi 4000

TOM LAI

Di cd mot cai nhin tdng quat ve cac phuong phap gan diing chiing la lap

mdt so dd (trang 22 )Theo so dd nay khi giai phuong trinh Schroedinger ihudng ngudi ta sir dung hai phep gan diing :

- Phep gan diing hau iTnh Bohr Oppenheimer

- Phep gan diing MO- LCAO

1/ Neu khdng sir dung nhiing phep gan diing khae chiing la se cd phuong phap khdng kinh nghiem AB- initio, edn ggi la phirong phap tfnh tu dau

Uu diam cua phirong phap nay la cho phep xac dinh dugc tai ca cac tfnh chai ciia phAn tu chi tu nhiing yen td chii yen cua bai loan nhu sd hat electron , dien tfch electron , so hat nhan, loai hat nhan ma khdng sir dung bai eii cac sd lieu thuc nghiem nao khae

2/ Khi sir dung den nhung phep gfin diing khae, da don gian bai loan la se cd cac phucmg phap ban kinh nghiem Cac phuong phap nay chia lam hai loai :

-I- Loai thu nhai danh cho tat ca cac electron hoac ft nhat cho nhung electron hoa tri cua cac hgp chat vd co hoac hiiu co

+ Loai thu hai chi danh cho cac hgp chai hiiu co cd he lien hgp electron

71 (xem so do )

1.4- Doi tugng nghien cOru cua de tai

Cling vdi su phat trien cua hoa hgc hiiu co, tu lau cac hgp chat di vdng da dugc nghian ciiru va ung dung trong nhiau nganh khoa hgc va ky thuSt khae nhau ciing nhu trong cuge sdng Ngay nay so cac hgp chat di vdng da vugt qua sd' cac

hgp cha't vdng carbon va khdng vdng Hang nam cac cdng trinh vi cac hgp chai di vdng chiem qua nua cac cdng trinh khoa hgc vi hda hgc huu co dugc cdng bd'

.Cac hgp chai di vdng ngay nay da dugc ap dung rgng rai trong cac nganh nhu hoa dugc, san xuat thude nhugm, nghian cijru cac hgp chat cd hoat tfnh sinh ly va hoa

sinh Tuy da dugc nghian cuu nhieu nhu vay, cho den nay cac nghian cuu vi mat

ly thuyet cac hgp chai di vdng van edn han che'

Hgp chai cu tha ma chiing tdi khao sat la day hgp chat a,P - xeton khdng no chiia nhan ihiophen vdi hai dang:

the' a vi trf para cua nhan phenyl Phan tu lugng cua hop chat = 214 +M^ g/mol

Trong phan khung -Cj^HgOS co chua bon loai nguyen tu C,H,0,S vdi t6ng s6 25 nguyen tu Neu theo ly thuyet c6 dian v6 lien ket dinh cu phan khung chiJa 10 li6n kd't C-H, con lai la 7 lien ket doi "=" va 8 lien ket dcm "—" Trong phan tir ta dac bidt quan tam den nhan phenyl co nhom the -X a vi trf para, di vong thiophen vk nhom carbonyl C=0 lien hgp vdi lien ket CH=CH

L4.1 Dac diam vi cau tnic cua hop chat khao sat (X-CMHQOS)

1.4.1.1 Nhan phenyl vd vi tri the para

Theo ly thuyet MO, cau tao cua benzen la mdt he thong lien hop 6 electron

pi He thong lian hgp nay lam cho benzen ban vung hon rat nhiau so vdi cac

cyclodien Do cd sir lian hgp ma cac lien ket tao thanh vdng cd dd dai ddng dau,

toan bd phan tir khdng phan cue va nam tran mot mat phang Do dai ciia cac lidn

ket trong cac hydrocarbon lian hgp ndi chung cd gia tri trung gian ciia cac gia tri

C-C va C=C trong he thdng cac hydrocarbon thdng thudng Vf du nhu :

Lian ka'l/kieu phan tu Do dai lian ket A°

C-C/phan tu chua nd'i ddi lian hgp phang 1.512

C=C/Phan tu chiJa nd'i ddi lian hgp phang 1.338

C-C /Phan tu benzen 1.395

Tu dd, sir thay doi do dai lian ka'l cung cho ta thay muc dd lian hgp ciia hgp

chai Nang lugng cua phan tu benzen cd the coi la mdt ham cua dd dai liSn ka't

Khi thay the mdt hydro trong phan tu benzen bang mdt nhdm the' X, nhdm the' X

se lam thay ddi loan bd sir phan bo ddng deu ciia cac electron pi trong ha thd'ng

lien hgp, qua dd lam thay doi tfnh chat hoa hgc, co che phan ung ciia pha tir Theo

ly thuyet cd dien, ngudi ta chia sir anh huong khi cd su phan bd' lai mat dd electron

trong phan tu thanh hai loai hieu ung chfnh

Hieu ling thu nhat la hieu ung cam ung ky hieu la I, cd hai dang + 1 va -I

tuong ling vdi sir day va hiit electron tao thanh lian ket Hieu ung nay tac ddng lan

lian kai a, xuai hien khi hai nguyan tu khae nhau va do am dien lian ka't vdi nhau

Kei qua cudi cung, lian ket a bi phan cue Cac nhdm the cd hieu lirng +1 bao gdm

cac ankyl , cirdng do cua hieu ung tang theo bac cua lien ket Cac nhdm tha'cd hidu

ung -I bao gdm cac halogen , cac -OR, -NR., -CR=CH2 Ddi vdi cac ha cd sii lian

hgp, cac nhdm the gay ra hieu ling lian hgp { +/- C) , dau + hay - tuong ung vdi sir

day hay hut electron Tfnh cha't cua hieu ung la ft thay d6i theo chi6u dai mach v^

chi CO tac dung tren mach phang D'ltu nay dugc giai thfch la do su lai hoa cua

cac electron pi ciia cac orbital p nam tromg mot mat phing xac dinh, nd'u lidn kd't

lien hgp vai no nam khae mat phang thi khong thi tao thanh he co xen phu cure dai

Cac nhom the halogen, NR2 , OR cho hieu ung+C, con cac lien ket C=0,

-CH=NH,-CH=CH2 lai the hien hieu umg -C Nhu vay doi voi mdt s6' nhom chuc,

CO hai hieu ung ngugc chi6u-I va +C nhu cac halogen

De dac trung cho anh huong t6ng cgng cac hieu ung Hammet co dua ra

mdt dai lugng la hang so Hammet ky hieu la a Cac nhom thd' co a > 0 nhom

the la hiit electron , cac nhom the G< 0 cho hieu ung day electron Gia tri tuySt

d6'i o cho bid't muc d6 anh huong cua nhom the Duod day la m6t vai gia tri ciia

hang so Hammet a cua mot so nhom the thudng gap :

Ten nhom the Gia tri hang so Hammet a

^NH^ -0.660 -OH -0.357 -0CH3 -0.268 -CH3 -0.17 -H 0.000 -F 0.060 -CI 0.227 -Br 0.232 -CN 0.660 -NO 0.780

Hang s6' Hammet a dugc xac dinh tir bieu thuc sau

k

Trong do :

log—= p.a (1.33)

ko va k la hang sd can bang cua phan ung phan ly a trang thai khdng va cd

nhdm the 6 cac vi trf meta hoac para

p - he sd', khdng ddi dd'i vdi mot dang phan tii, dac trung cho miic dd nhay cam ciia phan tu dd'i vdi cac nhdm tha

loo A chfnh la su bien ddi kha nang phan ung ciia cha't khi cd mat nhdm

the'

1.4.12 Nhan thiophen

Dd'i vdi qua trinh tfnh toan cac hgp chat di vdng bang cac phuong phdp ban kinh nghiem, chiing ta gap phai hai khd khan chfnh la xu ly su phan cue ciia lian kai a, va tim kiem cac tham so hgp ly Dd'i vdi cac hgp chat chi chiifa H,C, ta coi nhu cac lian kei sigma C-C la khdng phan cue, va do dd khdng lam anh huong da'n cac nguyan tu canh chiing Do dai lian kai don, ddi hoac kep ba cd the coi la khdng

ddi trong loan bd phan tu, diau nay da dang cho qua trinh tham sd hoa Dd'i v6\ cac

hgp cha't di vdng , cu the la nhan thiophen, vi nguyan td S cd dd am dien Idn hon nguyan to C, nan lian ket sigma S-C bi phan cue, lam anh huong den toan bd ca'u hinh electron cua he Cac tham so va do dai lien ket , nang lugng lian ka't ciia di t6

va C ndi chung la khd tim kiem hon so vdi cac hydrocarbon Thiophen la hgp cha't

di vdng chua mdt di to khdng bao hoa, chiing cd tinh cha't khae vdi cac xyclopentadien, va chiing cd tfnh chat lian hgp rd ret

Theo ly thuyet MO, thiophen cd cau true ddng phang vdi cdc nguyan tii C lai hoa kiau sp" Mdi mdt nguyan tu C lai hoa sp^ va mdt AO-p^ nguyan chiing , nhdm di to ddng gdp hai electron pi tao thanh he thd'ng sau electron thoa man cdng thuc Huckel ben viing Mac du he thd'ng vin dam bao qui tac ciia Huckel sd' electron pi tham gia lian hgp la 4n4-2, nhung trong thuc te' mdt minh S dimg hai electron tu do tham gia vao he lien hgp He thdng electron khdng phan bd' dau nhu benzen, dan den do dai cac canh cua lian ket khdng ddng dau Khi tfnh toan theo phuong phap MO-LCAO, AO cua electron thugc S phai nhan hai, va nhu vay

ma tran F se cd dang khdng nhu thdng ihudng Nguyan tu S van con hai electron

khdng tham gia vao he lian hgp, tro thanh nhdm cd kha nang day electron trong phan tu Hai vi trf 2 va 5 trong vdng thiophene cd kha nang tham gia cac phan ung

the electrophin nghTa la cd kha nang hiit electron Trong trudng hgp khdng c6

doan mach -CH-CH2CO thi vi trf so 2 se cd tfnh chat hiit electron Viae cd mat nhdm CO va nhan phenyl chua nhdm the paa X se cd tha thay ddi mat dd electron cua C2 va C5 va mat nang lugng , cac hgp chat di vdng thuong kem ban hon so vdi benzen ;

Thiophene

Trong ba hgp chai tren thi thiophen cd sir phan bd dien tfch dn dinh hon ca

Dd dd thiophen cd do ben hon , khi tham gia cac phan ling hoa hgc So vdi furan va pyrrole thi thiophen la dugc coi la khd mo vdng hon ca

Tliiophen trong cdng nghiep dugc diau che bang each ddng vdng butan, butadien hay buten vdi S [8], phan ung thudng dian ra khi ta dun hdn hgp tai 600

oC, phun qua dng phan ung rdi ngung lai

1.4 J 3 Nhom Carbonyl vd sir dich chuyen electron trong mach lien hap :

Trong lian ket cua nhdm chiic Carbonyl C=0, nguyan to O cd dd am dian

Idn hon do dd se hiit electron vi phfa minh, lam cho lian ket n bi phan cue, nhd su

lian hgp vdi nhdm C=C ma anh huong den nhan phenyl ddi vdi ca'u dang :

c=^c-c^

^6

Sir lien hgp nay cung dong thdi anh hirdng den sir phan bd

cetron trong nhan thiophen

dt each tuong tu la ciing cd buc Iranh lian hgp cua phan tu kiau B :

ach lian lurp lulu nhu Irict ticu

Nhdm the X d vi ti i the para do dd hfiu nhu khdng cd tuong tac true tid'p vdi idm the CO , ngoai ra o vi tri para nay hieu ling khdng gian cd tha bo qua guyan tu O cd tha cd cac tucrng tac vdi S trong nhan ihiophen d dang A:

a lam cho phAn lir kcni ben hon

Mat dd electron cd ihC tflp trung d nguyen t li O va nguyfin tir S Nhdm tha'

anh hucmg len nhan phenyl, do dd anh hirdng deii mat dd electron ciia nguyan tir

K mat dd electron tai cac lien kai C = 0 , C=C Cac vdng Ben zen va thiophen cung

I bi anh hirdng Ddi vdi mdi lian kai mat do electron cang cao thi do dai lian ka't

ang giiini

Va phd dao ddng, ddi vdi hgp chat khao sat cluing tdi irdng dgi sir cd mat lia cac dao ddng sau :

khdng tham gia vao he lian hgp, tro thanh nhdm cd kha nang day electron trong phan tir Hai vi trf 2 va 5 trong vdng thiophene cd kha nang tham gia cac phan ung the electrophin nghTa la cd kha nang hiit electron Trong trudng hgp khdng cd

doan mach -CH-CH.CO thi vi trf so 2 se cd tfnh cha't hiit electron Viae c6 mat

nhdm CO va nhan phenyl chiia nhdm the paa X se cd tha thay ddi mat dd electron cua C2 va C5 Ve mat nang lugng , cac hgp chat di vdng thudng kem ban hon so vdi benzen :

Trong ba hgp chai Iran thi thiophen cd sir phan bd' dian tfch dn dinh hon ca

Dd dd thiophen cd do ban hon , khi tham gia cac phan ung hoa hgc So vdi furan va pyrrole thi thiophen la dugc coi la khd mo vdng hon ca

Tliiophen trong cdng nghiep dugc diau che bang each ddng vdng butan, butadien hay buten vdi S [8], phan ung ihudng dian ra khi ta dun hdn hgp tai 600

oC, phun qua dng phan ung rdi ngung lai

1.4.1.3 Nhom Carbonyl vd sir dich chuyen electron trong mach lien hap :

Trong lian kai cua nhdm chiic Carbonyl C=0, nguyan td 0 cd dd am dien

Idn hon do dd se hiit electron ve phfa minh, lam cho lian ket % bi phan cue, nhd su

lian hc;rp vdi nhdm C=C ma anh huong den nhan phenyl ddi vdi ca'u dang :

AH kcal/mol

Su lien hgp ni\\ cung dong thdi anh lurang den su phan b6' lai mat dd

electron trong nhAn thiophen

MOt each tuong tu ta cung co buc Iranh lien hgp cua phan tu ki6u B :

Nhdm the X d \i tii the para do dd hfiu nhu khdng cd tuong tac true tia'p vdi

nhdm the CO , ngoai ra d vi tii para nay hieu ung khdng gian cd th^ bo qua Nguyan lir () cd the c() cac tucrng lac vdi S trong nhan thiophen d dang A:

X c=c-c

II

o s"

va lam cho phAn lii kem ban han

Mat do electron cd tha tap trung d nguNcn t li O va nguyen tir S Nhdm thS'

X anh lurcmg len nhan phenyl, do dd anh hudng den mat dd electron ciia nguyan tir

O, mat dd electron lai cac lien ket C = 0 , C=C Cac vdng Ben zen va thiophen cung

se bi anh huong Ddi vdi mdi lien kai mat do electron cang cao thi do dai lian ka't Ciing giam

v a phd dao ddng, ddi vdi hgp chai khao sal chiing Idi Irdng dgi su cd mat ciia Ciic diio ddng siui :

+ Dao dong C-C , Vc.c vao khoang 1100 - 1250 c m ' [11], su lien hgp se la

tang bac cua cac lien ket don va do do tang gia tri v

+ Dao dong C=C ,Vc=c vao khoang 1600 den 1670 cm"', su lien hgp se lam

giam bac lien ket do do v^^c se giam xuong khoang 1600 - 1640 cm"'

+ Dao dong hoa tri C-H, ,VC.H vao khoang 2900 - 3300 cm"'

Cac dao dong bien dang 5C.H phu thugc manh vao nhom the

+ Dao dong C-X tang theo do am dien cua nhom the X [6] vi du :

R CO hieu img-I, 1720 - 1765 (lam tang )

Co lien hgp 1660 - 1705 (lam giam )

CHLONG 2: PHAN THLC NGHIEM VA BIEN LUAN

KET QUA

2.1 Phan mem va cac budc tien hanh nghien ciiru :

Nhu da nau , phuong phap AB- initio la phuong phap cd the mang hii do

chfnh xac cao nhai, nhung phuong phap nay ddi hoi qua nhieu thdi gian va dung

lugng may tfnh Idn de thuc hien qua trinh linh loan Cac phuong phap ban kinh

nghiem cd tung do chinh xac riang cua nd tuy thude vao sir phii hgp ciia cac tham

sd va dieu kien hdi tu dua ra trong qua trinh thuc hien tinh toiin theo dai thuat

Irudng tuhgp SCF Vi du nhu vdi che do hoiit ddng chuan ciia MOPAC [13]

Phuong phiip Do dai( A") Gdc liankai ( ") A H ( kcal/mol)

MIND03 0,001 0.1 1 AMI 0.01 1

PM3 0.036 3.9 4.4-10

Hien nay Iran the gidi phat hanh rat nhiau cac phan mam cho phep ta giai

cac bai loan theo ca hai phuong phap AB- initio va cac phirong phap ban kinh

nehiem

*-Phrin mem cho phep chiing ta khao sat phan tu d cii trang thai hoi va trang

thai dung dich, o trimg thai vd ddng hoac trang thai vd md ( trang thiii kich thich )

0 ban luan van nay chung tdi sii dung phan mem HYPERCHEM phian ban 4.5

ciia cdng ly HYPERCUBE Inc Vi day la phan mem da sir dung , cd san va cd do

chinh Xiic phii hgp da thuc hien nhiem vu dat ra

Trong phep tdi uu hoii hinh hgc chiing tdi sir dung thuat loan Polak Rubiere

cua phuong phiip biin kinh nghiem AMI |23| ( gradient lian hgp ) Quii trinh khiio

siil sir bien ddi cua nang lugng se cho la mot cau hinh iriing thiii the nang ba mat

dat cue tiau so vdi cac lan can dugc khao say [20] dieu kien kai ihiic : 0.1 kcal/(A'' mol) ( su bien ddi nang lugng theo ba true X, Y, Z )

Trong phep tinh Single Point, khi su dung phuong phap AMI, chiing tdi sir dung cac diau kien :

Dien tfch = 0 Tdng so Spin = 1

Diau kien hdi tu :0.00lkcal/mol

So vdng lap tdi da trong thuat loan trudng tu hgp : 150

Trang thai kfch thfch cua cac electron hoa tri trong phan tii : thap nhai

Cap ddi Spin : phuong phap UHF ( Unrestricted Hatree Fock )

Khi sir dung phuong phap tfnh Single point bang phuong phap ZINDO/S :

He sd sua ddi ddi vdi cac tfch phan cdng hudng [5,j ;

+ Sigma - sigma ; 1.267 + Pi- Pi : 0.64

2.2 Cac birdc chung toi tien hanh tinh toan khao sat co the bao gom

01 Dung cac c^u hinh co the d6'i vai hai dang alpha( A) va be ta

(B) l6'i iru hoa hinh hoc bang phirong phap AMI

8 thi nghiem \ai S ciiu dang

Lua chon phuang phap theo nang lucmg lien kei nhiei hinh

thanh doi vai 1 phan tu

Cac phuang phap su dung : CNDO INDO, MINDO,

MINDO/3, AMI, PM3 ZINDO ZINDO/S

Tim cau dang ben nhat A va B xac dinh cac thong so hinh

hoc ph^n tu gian do spin, electron ciia phin tir

Theo ca hai phuang phap ZINDO/S va AMI

8 thf nghiem, ket luan : -tinh loan E.Delta H, : phuang phap ZINDO/S

-Tinh toan momen luong cue/ pho dao dong : phuang phap AMI

Khao sat su keo dai mach :

Kei luan Phan tu B2 A4

T6\ uu hinh hoc phan tu A4-X va B2-X trong do X la cac

20 thf nghiem vai phan tu A4-X

va B2 X hang phuang phap AMI

Ti'nh loan cac thong so luang lu nhu nang luong lien ket,

nhiet tao thanh momen luong cue cac thong so hinh hoc

phan tir cua cac phan lir A4-X va B2-X

56 thf nghiem vai phuang phap ZINDO/S ( nhom the -Br va -CI khong Ifnh dugc bang phuang phap ZINDO/S Tfnh moment luang cue bAng phuang phap PM3

07 T'nh loan dao dong ciia nguyen tir trong phan lir pho hong

ngoaiilR) cua cac phan lir A4-X va B2-X

T6ng cong so ihi nghiem

IX thf nghiem bang phmrng phap AMI

160

2.3 Chon phirong phap

Nhir da neu a phdn trdn, hien nay co r^'t nhieu phuong phap tinh gan dung De bat

dau khao sat anh hirong cua cac nhom the len day cac hop cha't a,p xeton kh6ng no chiia di vong thiophen, chung t6i ti^n hanh tfnh thu theo cac phuog phap hien co de tim ra mot phucmg phap tfnh phii hop

Cac phuang phap tfnh gan dung nay cho cac bo cac ket qua khae nhau Ngoai ra, d6i voi tung day cha't cu the, se co cac phuong phap phu hop Ta biet rang trong phien ban HYPERCHEM 4.5 co t6n tai tam phuong phap tfnh gdn dung, trong do hai phuong phap ZINDO/1 va ZINDO/S khdng co kha nang t6'i uu hoa hinh hoc va phan tfch dao d6ng Dua vao lich su phat trien cac phuong phap, ddu tien chiing t6i th6ng nhat sir dung phucmg phap AMI de toi uu hod hinh hoc phan tir Phan tir duoc diing de khao sat va xac dinh phuong phap tfnh la phan tir Al, co dang :

Sau do Idn luot sir dung tam phuomg phap de tfnh toan cac thong sd tuong tir Cac thong s6 : nang luong lien ket, nhiet hinh thanh va mdment luong cue Ket qua thu duoc dugc thong ke trong bang 2.1, va bieu dien bang bieu do 2.1, 2.2 Cac ket qua tfnh toan cu the luu o phdn phu luc I

Bang s62.1 : Ket €^^4phafttich-ItfechoA phuong phap

Occal/mol) -H349-.5-28 -8111.915 -2K2I.K09 -2814.190

- 2 8 1 9 ^ 3

Naftg luoftg (^cal/mol) -34^57<h232 -339117.688 -29027^.964 -284099.963 -282143-902

Nhiet hinh thanh fkcal/mol) -5480.979 -5243.366 46.740 53.609 49.316

lUGcng cuc(D) 5.248 6.301 3.735 6.178 3.637

-2825.255 -8325^81 -10837.482

-288856.707 -334953.313 -261849.807

43.294 -5456.732

-7968-933

2.958 6.147 7.259

nhj^t h'mh th^h

( kcal/mol )

NHlfeT HINH THANH

-8000 -6000 -4000 -2000

Biau d6 2.1 : Sir phu thu6c cua nhiet hinh thanh vao phiiorng phap tmh

Nang lUfWig li*n k6i {kcalAnol )

NANG Ll/ONG LifiN k f T

o

S ^ s

Z O Q- <

Bie\i d6 2.2 : Sir phu thuoc ciia nang laong lien ket vao phircmg phap tfnh

Dira vao ket qua ta thdy, trong tam phirong phap thi phircmg phap ZINDO/S cho cac kei qua la nang luong lien ket va nhiet hinh thanh nho nhat, cac gia tri deu mang ddu am, phu hcrp vai ly thuyet nhiet hoa hoc Cac phirang phap MNDO, MIND03, PM3, AM! tfnh toan va cho ra ket qua nhiet hinh thanh dirang, trai vai