Sains Malaysiana  37(2): 201-203(2008)

Synthesis and Characterisation of Tris(1-carboxyl-2-phenyl-1,2-ethyleno dithiolenic-S,S’) Tungsten Complex as Photocatalyst for Photolysis

of H₂O Molecules

(Sintesis dan Pencirian Kompleks Tris[1-karboksil-2-fenil-1,2-etilenoditiolenik-S,S’]

Tungsten sebagai Fotomangkin untuk Fotolisis Molekul H₂O)

Fadhli Hadana Rahman, Rusli Daik & Mohammad Kassim

School of Chemical Sciences and Food Technology

Faculty of Science and Technology, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, Malaysia

Khuzaimah & Wan Ramli Wan Daud

Department of Chemical and Process Engineering

Faculty of Engineering, Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, Malaysia

Received:  4 April 2007 / Accepted: 13 July 2007

ABSTRACT

Tris(1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S’) tungsten complex is one of the most promising photocatalyst to be used in photolysis of water to produce hydrogen. The first step of the synthesis involves a metathesis reaction of tetrapropylammonium bromide [{(C₃H₇)₄N}Br] and ammonium tetrathiotungstate [(NH₄)₂WS₄] to form a tetrapropylammonium tetrathiotungstate [{(C₃H₇)₄N}₂WS₄] (precursor). Then, the precursor was reacted with phenylacetylenecarboxylic acid (C₉H₆O₂) to form tris(1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S’) tungsten complex (C₂₇H₁₈O₂S₆W). The infra-red, ultra violet/visible (UV/Vis) spectrum, nuclear magnetic resonance (NMR) and elemental micro-analysis of C, H, N and S agreed with the characteristic of the tris(1-carboxyl-2-phenyl-1,2-ethylenodithiolenic-S,S’) tungsten complex. The (W-S), (C-S) and (C=O) stretching frequencies were detected at 511, (1470 and 1035) and 1655 cm^-1, respectively. The ¹H NMR spectrum showed six protons in the complex. The ¹³C NMR showed only 7 signals for carbon atom in the benzene ring, ethylene groups and carboxylic acid pendant group due to the symmetry of the molecules. The reaction yield was about 50 percent. Photolysis of acetone spiked H₂O showed that the catalyst was able to produced 1.8µmol/h hydrogen.

Keywords: dye-sensitised solar cell; hydrogen; photolysis; sunlight; tungsten

ABSTRAK

Kompleks tris(1-karboksil-2-fenil-1,2-etilenoditiolenik-S,S’) tungsten merupakan salah satu daripada kompleks yang berpotensi tinggi untuk digunakan bagi proses fotolisis air untuk menghasilkan gas hidrogen. Langkah pertama sintesis melibatkan tindak balas metatesis di antara tetrapropilammonium bromida [{(C₃H₇)₄N}Br] dan ammonium tetratiotungstat [(NH₄)₂WS₄] untuk menghasilkan tetrapropilammonium tetratiotungstat [{(C₃H₇)₄N}₂WS₄] (prekursor). Seterusnya prekusor bertindak balas dengan asid fenilasetilenakarboksilik (C₉H₆O₂) dan membentuk kompleks tris(1-karboksil-2-fenil-1,2-etilenoditiolenik-S,S’) tungsten (C₂₇H₁₈O₂S₆W). Molekul telah diciri dengan kaedah spketroskopi inframerah (IR), ultraviolet/boleh nampak (UV/Vis), resonans magnet nuklear (NMR) dan analisis-mikro unsur C, H, N dan S. Spektrum IR menunujukkan kehadiran frekuensi regangan (W-S), (C-S) dan (C=O) masing-masing pada 511, (1470 dan 1035) dan 1655 cm^-1. Spektrum NMR ¹H menunjukkan kehadiran 6 proton kumpulan propil dan spektrum NMR ¹³C hanya menunujukkan 7 atom C bagi gelang benzena, etilena dan asid karbosilik. Hanya bilangan setara isyarat resonans ¹H dan ¹³C dikesan kerana struktur mempunyai satah simetri yang tinggi. Peratus hasil kompleks agak rendah (50%) disebabkan kesukaran untuk memisahkan isomer yang terbentuk. Ujian fotolisis air yang dicampur aseton memnunjukkan kemampuan fotomangkin untuk menghasilkan  hidrogen pada kadar 1.8µmol/j.

Kata kunci: bahan pewarna-pemeka sel solar; hidrogen; fotolisis; sinaran matahari; tungsten

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