hydrothermal synthesis and crystal structure of a novel one - dimensional tritungstate

Hydrothermal synthesis and crystal structure of a novel one-dimensionalBangbo Yan, Yan Xu , Ngoh K.. The structure of title compound consists of infinite chains running parallel to the b

Hydrothermal synthesis and crystal structure of a novel one-dimensional

Bangbo Yan, Yan Xu)

, Ngoh K Goh, Lian S Chia

DiÕision of Chemistry, School of Science, Nanyang Technological UniÕersity, 469 Bukit Timah Road, Singapore 259756, Singapore

Received 21 February 2000

Abstract

Ethylenediammonium tritungstate, C H N2 10 2 W O3 10, has been hydrothermally synthesized and structurally characterized The

structure of title compound consists of infinite chains running parallel to the b axis, that are made up of distorted WO octahedra linked6

through shared corners and edges The ethylenediammonium ions occupy interstrand region providing space-filling and charge-compensa-tion to anionic tritungstate matrix q 2000 Elsevier Science S.A All rights reserved.

Keywords: Hydrothermal synthesis; Tungstate; Crystal structures; Polyanions compounds

1 Introduction

Recent years have witnessed a considerable

achieve-ment in the crystal engineering of novel organicrinorganic

hybrid materials due to their applications in catalysis,

sorption, energy storage, molecular electronics, optical

ma-w x

terials and ceramics 1–4 A promising synthetic route

takes advantage of a low-temperature soft approach,

hy-drothermal method, and the structure-directing function of

organoamines Recent developments in this area have

proven its viability for the successful preparation of novel

w x

porous and low-dimensional materials 5–7 Typical

ex-amples include coorperative assembly of organic

w x

aminesrtransition metal oxides involving iron 8,9 , cobalt

w10 , vanadium 11 and molybdenum 5,12,13 While thex w x w x

combined application of hydrothermal crystallization and

amine templates has been extensively exercised for the

assembly of periodic elements, systematic investigation of

tungsten oxide composite materials remains largely

unex-plored Here, we report the hydrothermal assembly and

Ž

crystal structure of a novel one-dimensional tritungstate VI

solid structurally directed and stabilized through

diammonium ions, C H N2 10 2 W O3 10 1.

)

Corresponding author Tel.: q65-460-5179; fax: q65-469-8952.

E-mail address: yxu@nie.edu.sg Y Xu

2 Experimental

2.1 Synthesis

A gel mixture of Na WO P 2H O 0.67 g, 2 mmol ,2 4 2

ethylenediamine en 0.42 g, 7 mmol and H O 20 ml,2

1.11 mol in the mole ratio 1:3.5:555 was heated at 1908C and autogenous pressure conditions for 62 h Needle-shape

colorless crystals of C H N2 10 2 W O3 10 1 were isolated

Ž

and recovered yield: 0.37 g, 48% based on Na WO P2 4

2H O The CHN elemental analysis of 1 gave observed2

Žcalculated in wt% C, 3.02 3.10 ; H, 1.29 1.30 ; N, x Ž Ž

3.61 3.62 which confirmed an empirical formula of

ŽC H N2 10 2.wW O3 10xfor 1.

2.2 Thermal analysis

Thermogravimetric analysis TGA was performed us-ing a Sateram TG-DTGrDSC thermogravimetric analyzer

on powder specimen of 1 at a heating rate of 58C miny 1 in

N stream.2

2.3 Infrared studies

IR spectra were recorded using a Perkin–Elmer FT–IR spectrophotometer on KBr pellets in the range 400–4000

cmy 1

1387-7003r00r$ - see front matter q 2000 Elsevier Science S.A All rights reserved.

PII: S 1 3 8 7 - 7 0 0 3 0 0 0 0 0 8 5 - X

Ž w x

Fig 1 Packing view of C H2 10N2 W O3 10 1 along the b-axis.

2.4 X-ray Crystallographic Studies

X-ray crystallographic data of 1 were collected on

a Siemens P4 diffractometer Crystal data: monoclinic

P2 1 r n, a s 8.9512 10 , b s 7.6483 11 , c s 16.005 3

A, b s 92.020 14 8, V s 1095.0 3 A , Dcalcs4.693 g

cmy 3

and Z s 4 The structure was solved by direct

methods and refined using full-matrix least squares on F2

w x

using the SHELXTL-97 package 14 Non-hydrogen atoms

were refined with anisotropic temperature factors

Hydro-gen atoms were placed at calculated positions and refined

using the riding model of SHELXTL program with a fixed

˚

C–H bond length of 0.97 A and a N–H bond length of

˚

0.90 A Final refinement was based on 1917 reflections

wI ) 2 s IŽ xfor 134 parameters and converged to R wR1Ž 2

s0.0281 0.0634 Atomic coordinates, bond lengths and

angles and thermal parameters are presented in

supplemen-tary crystallographic data

3 Results and Discussion

The title compound is initially isolated from the

hy-drothermal reaction of WO , en, NaOH and H O in3 2

polycrystalline form Replacement of NaOH with LiOH

produces the same crystalline phase with similar product

quality and morphology The reaction is then rationalized

by using Na WO as W2 4 6q source instead of WO that3

gives rise to monophasic product of compound 1

contain-ing large scontain-ingle crystals TGA shows a weight loss of ca

7.9% in the temperature range 300–4808C indicating the

release of en molecules calc, 8.0% The infrared spectra

of 1 present the following information: strong absorption

bands at 935 and 975 cm are ascribed to Õ W s O , and the features in the 784–889 cmy 1

region are most likely

associated with Õ O–W–O modes In addition, absorption bands at 1480 and 1624 cmy 1

, and a broad band centred at

3400 cmy 1

suggest the presence of en species By replac-ing en with other organodiamines such as 2,2X-bipyridine

Ž2,2 -bipy , piperazine, and 4,4’-bipyridine, a few newX

organicrinorganic hybrid phases are obtained and struc-turally identified using the single crystal X-ray diffraction method Brief crystal data of one of the phases, a

Fig 2 Structural building block W O of C H N W O 1.

Fig 3 Comparison of the one-dimensional chains adopted by the anions

in: a C H2 10N2 W O3 10 1; b C H2 10N2 Mo O3 10 15 ; and c an

w x w x

open framework solid K W O2 3 10 16

clinic one-dimensional solid WO 2,2 -bipy , are summa-3

rized in a footnote1

The structure of C H N2 10 2 W O3 10 1 consists of

infi-nite puckered chains of W O6 4y20 separated by interstrand

ethylenediammonium ions, C H N2 10 2 enH2 , as shown

in Fig 1 The W6q sites exhibit distorted octahedral

geometry which receive contributions from 1-, 2- and

4-coordinated oxo groups Each W O6 4y20 unit consists of a

pair of center-of-symmetry-related W O3 10 trimers of

edge-sharing WO octahedra as shown in Fig 2 Adjacent6

W O6 204y units are connected by sharing two corners giving

rise to the infinite chain of 1 lying parallel to the b-axis.

Ž

The coordination geometry of WO at W 1 is defined by6

two terminal oxo groups and four unsymmetrical bridging

oxo groups, and at W 2 and W 3 by one terminal oxo

Ž

group and five unsymmetrical bridging oxo groups W 1

site shows typical two short-two intermediate-two long

bond length pattern of tungsten VI oxides, and W 2 and

Ž

W 3 show one short-three intermediate-two long bond

length pattern enH2q2 cations occupy interstrand regions

of the W O6 204y chains and exhibit strong hydrogen bond

network to terminal and bridging oxo groups of the anionic

chains of W O6 204y

1

Ž X .

Crystal data for the monoclinic WO 2,2 -bipy3 phase chemical

formula, C10H N O W, M s 388.03, monoclinic space group Cc with8 2 3 w

˚

unit cell dimensions as14.323 3 , bs9.608 2 , cs 7.2922 15 A, b s

101.980 16 8, V s981.6 4 A , Zs 4, D s 2.626 g cm c , m s11.759

mm -1, T s 297 K.

The linkage between WO6 octahedra in 1 is quite

distinct from those reported in C H N2 10 2 Mo O3 10 15

ŽFig 3 b The anionic chain of W OŽ 6 4y20 of 1 is

con-structed from corner- and edge-sharing WO6 octahedra while the one-dimensional chains of Mo O6 4y20 of

ŽC H N2 10 2.wMo O3 10x w15 is built up from MoO octahedrax 6

through shared corners, edges and faces It should be

further noted that compound C H N2 10 2 W O3 10 1

re-ported in this paper is not analogous to a known tritungstate

phase, K W O2 3 10 16 , in which W O3 10 anions are orga-nized into a three dimensional covalent framework

struc-Ž

ture through corner- and edge-shared WO octahedra Fig.6

Ž

3 c

The one-dimensional tritungstate C H N2 10 2 W O3 10 1

reported in this paper provides novel examples to the hydrothermal cooperate assembly of tungsten oxide com-posite materials The strong solvating effect of water in combination with the structure-directing role of organoamines under the hydrothermal autogenous condi-tions evidently provides the conducive environment for the rearrangement of tungstenoxoanions, and construction of novel solid architecture from molecular precursors It opens

up the possibility of applying this method for assembling other low-dimensional and open-framework tungsten oxide materials with potentially interesting or useful properties

4 Conclusion

The successful synthesis of compound C H N2 10 2

wW O3 10x1 illustrates the power of hydrothermal synthesis

in engineering organicrinorganic solid materials with novel structures It should be further noted that organic cations play a significant role in the isolation of the tritungstate phases Furthermore, the structure differences between

ŽC H N2 10 2.wW O3 10x 1 and open-framework potassium

tritungstate, and that between C H N2 10 2 W O3 10 1 and

ethylenediammonium trimolybdate solids suggests that it would be worth exploring the hydrothermal chemistry of organicrtungsten oxide hybrid materials

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