A novel bimetallic double thiocyanate-bridged ruthenium and tungsten metal complex containing bipyridyl and dithiolene co-ligands was synthesized and the behavior of the complex as a dye-sensitizer for a photoelectrochemical (PEG) cell for a direct water splitting reaction was investigated. The ligands and metal complexes were characterized on the basis of elemental analysis as well as uv-Vis, Fourier transform infrared ( Pim) and nuclear magnetic resonance (11I and 13C NMR) spectroscopy. Cyclic voltammetry of the bimetallic complex showed multiple redox couples, in which half potentials E 112 at 0 .625 , 0.05 and 0.61 V were assigned as the formal redox processes of Ru(III)IRu(II) reduction, W(IV)IW(V) and W(V)IW(VI) oxidations, respectively. Photocurrent measurements were performed in homogeneous system and TiO2 was used as the photoanode for photocurrent measurements. Current density generated by the bimetallic complex was higher than that of N3 commercial dye which suggested that the bimetallic complex donated more electrons to the semiconductor.
Kompleks Ru(II), [Ru(bpy)2(pypzH)](PF6)2 dengan bpy = 2,2’-bipiridil dan pypzH= 2-(1H-pirazol-3-il)piridin, telah berjaya disintesis dan dicirikan dengan teknik spektroskopi transformasi Fourier inframerah (FTIR), ultralembayung dan cahaya nampak (UV-Vis), resonans magnet nukleus (RMN), serta spektrometer jisim. Pengiraan dengan kaedah teori fungsi ketumpatan (DFT) dan DFT bersandar masa (TD) telah dijalankan untuk membangunkan struktur optimum dan elektronik kompleks Ru(II). Data yang diperoleh menunjukkan orbital molekul terisi dengan tenaga tertinggi (HOMO) disetempatkan pada logam Ru(II) dan ligan pypzH, manakala orbital molekul tidak terisi dengan tenaga terendah (LUMO) didapati tersebar secara menyeluruh pada kedua-dua struktur ligan bpy. Aktiviti fotomangkin kompleks telah diuji terhadap penguruaian pewarna tekstil bromotimol biru (BTB) disebabkan aktiviti foto [Ru(bpy)2(pypzH)](PF6)2 di bawah sinaran lampu xenon 450W (AM 1.5, penapis inframerah). Kadar dan tertib tindak balas foto-uraian BTB dikenal pasti dan dibincangkan bersama dengan mekanisma foto-uraian BTB.
Aroylthiourea ligands, 1-aroyl-3-cyclohexyl-3-methylthiourea (HL1
), 1-(2-chloroaroyl)-3-cyclohexyl-3-methylthiourea
(HL2
), 1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3
) and 1-(4-chloroaroyl)-3-cyclohexyl-3-methylthiourea
(HL4
) were synthesized through a condensation reaction of methylcyclohexylamine and aroylisothiocyanate with a
general formula (X-Ph)(CO)NH(CS)N(C6
H5
)(CH3
) where X = H, o-Cl, m-Cl and p-Cl, fully characterized by CHNS micro
elemental analysis, infrared spectroscopy, UV-visible, nuclear magnetic resonance (1
H, 13C) and X-ray crystallography.
1-(3-chloroaroyl)-3-cyclohexyl-3-methylthiourea (HL3
) crystallized in the monoclinic system, a=14.504(3), b=4.9599(11),
c=22.325(5) Å, β=98.461(7)°, Z= 4 and V=1588.5(6) Å with space group P21
/c. The IR spectra of the ligands exhibits
the characteristic v(CO) and v(N-H) at range 1701-1640 cm-1 and 3317-3144 cm-1, respectively. Whereas the 1
H and 13C NMR spectra shows the resonances for N-H and -CO groups at range 8.3-8.5 and 160-163 ppm, respectively. A onepot reaction involving the aroylthiourea ligand, oxovanadium(IV) ion and potassium hydrotris(3,5-dimethylpyrazolyl)
borate (KTp*) complex gave the desired [oxovanadium(IV)(tris(pyrazolyl)borate)(aroylthiourea)] complexes namely
Tp*VOL1
, Tp*VOL2
, Tp*VOL3
and Tp*VOL4
and all complexes were characterized accordingly. X-ray study showed that
Tp*VOL1
adopted a monoclinic crystal, a=3.415(2), b=19.463(3), c=14.22(3) Å, β=107.411(4)°, Z= 4 and V=3542.7(11)
Å with P21
/c space group. The VO2+ center adopted a pseudo-octahedral geometry O2N3S, with the oxovanadium(IV)
coordinated to the bidentate ligand (X-Ph)(CO)NH(CS)N(C6
H5
)(CH3
) and tridentate Tp* ligands. The results showed
that aroylthiourea ligands behave as bidentate chelate through O and S atom and the Tp* C3v symmetry adds stabilization
to the VO2+ through its protective tripodal geometry.