 |
 |
 |
 |
 |
 |
Sifat Foto-Kimia Kompleks Molibdenum
Ditiolena
(Photo-Chemical
Properties of Molybdenum Dithiolene)
Mark Lee Wun Fui, Lorna Jeffery Minggu & Mohammad
B. Kassim*
Pusat
Pengajian Sains Kimia dan Teknologi Makanan, Fakulti Sains dan Teknologi
Universiti
Kebangsaan Malaysia, 43600 UKM Bangi, Selangor D.E. Malaysia
Diserahkan: 29 Jun 2011 / Diterima:
2 November 2011
ABSTRAK
Faktor yang perlu diberi perhatian bagi
bahan pemeka foto yang baik adalah keamatan serapan dan kedudukan serapan
spektrum elektronik dalam julat cahaya nampak, keupayaan redoks dan
kestabilan-fotonya. Kompleks molibdenum ditiolena dengan formula am
[MoTp*(NO)(L)] dengan Tp* = tris(3,5-dimetilpirazolil)hidroborat dan L =
toluena-3,4-ditiolat (L1); 1,2-benzenaditiolat
(L2);
3,6-dikloro-1,2-benzenaditiolat (L3)
didapati mempunyai sifat-sifat kimia dan fizik yang diperlukan untuk dijadikan
sebagai anod pemeka-foto-elektron untuk sel foto-elektrokimia penguraian
molekul air kepada hidrogen dan oksigen. Kompleks Mo-ditiolena yang disintesis
daripada prekursor [MoTp*(NO)(I)2] dan
sebatian ditiol dengan kehadiran Et3N sebagai
agen penurunan dan penyahprotonan telah diciri dengan menggunakan kaedah
analisis mikro unsur CHNS, spektroskopi IR,
ultra-lembahyung dan cahaya nampak (UV-Vis), dan elektrokimia. Puncak
penyerapan UV-Vis (λmax/ nm) dikesan pada
321-331, 369-372, 576-589 dan 736-741nm. Sifat keaktifan foto-kimia dan
foto-fizik turut dikaji bagi menentukan kesesuaiannya sebagai bahan pemeka foto
bagi sel foto-elektrokimia. Ujian kestabilan-foto menunjukkan tiada berlaku
penguraian terhadap ketiga-tiga kompleks tersebut selepas sinaran cahaya selama
24 jam.
Kata kunci: Bahan pemeka foto;
kestabilan-foto; molibdenum ditiolena
ABSTRACT
The important factors for a good
photosensitizer are intensity and position of the spectral absorption in
visible region, redox potentials and photo-stability. Molybdenum dithiolene
complexes with a general formula [MoTp*(NO)(L)] where Tp* = tris(3,5-dimethylpyrazolyl)hidroborate
and L = toluene-3,4-dithiolate (L1);
1,2-benzenedithiolate (L3);
3,6-dichloro-1,2-benzenedithiolate (L3) were
found to exhibit the required chemical and physical properties as an anode for
photo-electron-sensitizer to generation hydrogen and oxygen via water splitting
in photo-electrochemical cell. Mo-dithiolene complexes were synthesized from
the precursor [MoTp*(NO)(I)2] and dithiol compound
in the presence of Et3N as reducing and
deprotonating agents. These complexes were characterised by micro-elemental
analysis for CHNS, infrared and UV-Vis
spectroscopy, and electrochemical analysis. UV-Vis absorption peaks were
detected at 321-331, 369-372, 576-589, 736-741 nm (λmax/ nm).
The photo-chemical and photo-physical reactivities were studied to determine
the suitability of these complexes as photosensitizers in photo-electrochemical
cells. The photo-stability test showed no significant degradation of the
complexes after 24 h of light illumination.
Keywords:
molybdenum dithiolene; photosensitizer; photo-stability
RUJUKAN
Alobaidi, N., Chaudhury, M.,
Clague, D., Jones, C.J. & Pearson, J.C., McCleverty, J.A. & Salam S.S.
1987. Monometallic, homo- and hetero-bimetallic complexes based on redox active
tris(3,5-dimethylpyrazolyl)borato-molybdenum and -tungsten nitrosyls. Part 4.
The effects of ligating atom type on the reduction potentials of monometallic
complexes. Journal of the Chemical Society, Dalton Transactions (7):
1733-1736.
Alobaidi, N., Jones, C.J.
& McCleverty, J.A. 1989. Chelate complexes containing the
{Mo(NO)HB(3,5-Me2C3N2H)3} moiety and an example of a pyrazole substitution
reaction involving the HB(3,5-Me2C3N2H)3 ligand. Polyhedron 8:
1033-1037.
Falaras, P., Mitsopoulou,
C.A., Argyropoulos, D., Lyris, E., Psaroudakis, N., Vrachnou, E. & Katakis,
D. 1995. Synthesis, cyclic voltammetric and electrospray mass spectrometric
studies of a series of tris-substituted 1,2-dithiolene complexes of tungsten
and molybdenum. Inorganic Chemistry 34: 4536-4542.
Fujishma, A. & Honda, K.
1972. Electrochemical photolysis of water at a semiconductor electrode.
Nature 238 : 37-38.
Greenwood, N.N. &
Earnshaw, A. 1984. The Chemistry of the Elements Oxford, UK: Pergamon
Press.
Joshi, H.K., Inscore, F.E.,
Schirlin, J.T., Dhawan, I.K., Carducci, M.D., Bill, T.G. & Enemark, J.H.
2002. Six-coordinate molybdenum nitrosyls with a single ene-1,2
–dithiolate ligand. Inorganica Chimica Acta 337: 275-/286.
Katakis, D., Mitsopoulou, C.
& Konstantatos, J. 1992. Photocatalytic splitting of water. Journal of
Photochemistry and Photobiology A: Chemistry 68: 375-388.
Lyris, E., Argyropoulos, D.,
Mitsopoulou, C.A., Katakis, D. & Vrachnou, E. 1997. New catalyst in the
photo-oxidation of water. Journal of Photochemistry and Photobiology A:
Chemistry 108: 51-54.
McCleverty, J.A., Seddon, D.,
Bailey, N.A. & Walker, N.W. 1976. The chemistry of cyclopentadienyl and
related nitrosyl complexes of molybdenum. Part V.
Dihalogenonitrosyl[tris(pyrazolyl)borato]molybdenum complexes, their
alcoholysis, and the crystal structure of
chloronitrosylisopropoxo[tris(4-chloro-3,5-dimethylpyrazolyl)borato]molybdenum. Journal of the Chemical Society, Dalton Transactions (10): 898-908.
McCleverty,
J.A. & Ward, M.D. 1998. The role of bridgind ligands in controlling
electronic and magnetic properties in polynuclear complexes. Accounts of
Chemical Research 31: 842-851.
Mueller-Westerhoff U.T., Vance, B. &
Yoon, D.L. 1991. The synthesis of dithiolenes dye with strong near-IR
absorption. Tetrahedron 47(6): 909-932.
Wlodarczyk, A., Maher, J.P., Coles, S.,
Hibbs, D.E., Hursthouse, M.H.B., Abdul Malik & K.M. 1997. Oxo-bridged
binuclear molybdenum nitrosyl halides: structural and redox studies,
mixed-valence behavior, and characterisation of mononuclear hydroxo precursors.
Journal of Chemical Society, Dalton Transaction (15): 2597-2606.
*Pengarang untuk surat-menyurat; email: mbkassim@ukm.my
|
|||
|
