Browsing by Author "Kiran Diwan"

Now showing 1 - 7 of 7

Enhanced light harvesting efficiencies of bis(ferrocenylmethyl)-based sulfur rich sensitizers used in dye sensitized TiO 2 solar cells
(2012) Santosh K. Singh; Ratna Chauhan; Bandana Singh; Kiran Diwan; Gabriele Kociok-Köhn; Lal Bahadur; Nanhai Singh
In this work, the photosensitizing properties of ferrocene (Fc)-based compounds FcCH 2CS 3CH 2Fc (1) and FcCH 2SSCH 2Fc (2) were investigated and significant enhancement in the light harvesting efficiency was observed compared to those achieved with previously reported compounds from our lab. The compounds were fully characterized by spectroscopy and X-ray crystallography, and their electrochemical properties studied. DSSCs based on these dyes display efficiencies comparable to those of a standard cell based on N719 under similar experimental conditions. These studies demonstrate that ferrocenyl-based sulfur rich compounds with proper orientation of the Fc groups assisted via suitable linkers, together with desired redox properties and visible region electronic absorption features could constitute a new class of photosensitizers targeting light driven reactions. © 2012 The Royal Society of Chemistry.
Facile in situ copper(ii) mediated C-S bond activation transforming dithiocarbimate to carbamate and thiocarbamate generating Cu(ii) and Cu(i) complexes
(2012) Kiran Diwan; Bandana Singh; Santosh K. Singh; Michael G. B. Drew; Nanhai Singh
Facile in situ Cu(ii) mediated transformation of p- tolylsulfonyldithiocarbimate in conjunction with polypyridyl or phosphine ligands into corresponding carbamate and thiocarbamate led to the formation of new copper complexes with varying nuclearities and geometries, via C-S bond activation of the ligand within identical reaction systems. © 2012 The Royal Society of Chemistry.
Light harvesting properties of some new heteroleptic dithiocarbimate- diamine/diimine complexes of Ni, Pd and Pt studied as photosensitizer in dye-sensitized TiO2 solar cells
(Royal Society of Chemistry, 2014) Kiran Diwan; Ratna Chauhan; Santosh K. Singh; Bandana Singh; Michael G. B. Drew; Lal Bahadur; Nanhai Singh
This contribution describes the light harvesting efficiencies of new heteroleptic complexes of the form [M(L)(L′)] where L = p-tolylsulfonyldithiocarbimate (p-CH3C6H 4SO2NCS22-); M = Ni(ii), L′ = 2,2′-bipyridine (bpy) (1) or 1,10-phenanthroline (phen) (2) or N,N,N′,N′-tetramethylethylenediamine (tmed) (3); M = Pd(ii), L′ = bpy (4) or phen (5) or tmed (6); and M = Pt(ii), L′ = bpy (7) or phen (8) or tmed (9). These have been characterized by elemental analysis, IR, 1H and 13C NMR and UV-visible spectroscopies, and 1, 4 and 6 by single crystal X-ray diffraction. UV-visible absorption, electrochemical behavior and structural features of the ligand aromatic sulfonyldithiocarbimate containing free sulfonyl oxygen atoms serving as a typical anchoring group on TiO2 semiconductor electrode of the nickel complexes enable them to act as potential photosensitizers for solar energy conversion. This study widens the scope for square planar heteroleptic complexes with a suitable combination of metal ions and ligands to be explored as photosensitizers. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014.
Monometallic salts derived from complex anions of group 10 metal ions with p-tolylsulfonyldithiocarbimate ligand: Synthesis, characterization and properties
(2012) Santosh K. Singh; Kiran Diwan; Michael G.B. Drew; Nanhai Singh
New monometallic complex salts of the form X 2[M(L) 2] [M = Ni 2+, X = (CH 3) 2NH 2 +(1); M = Ni 2+, X = (CH 3) 4N + (2); M = Ni 2+, X = (C 2H 5) 4N +(3); M = Ni 2+, X = (C 3H 7) 4N +(4); M = Ni 2+; X = (C 6H 13) 4N +) (5); M = Pd 2+, X = (CH 3) 2NH 2 +(6); M = Pd 2+, X = (C 2H 5) 4N +(7); M = Pd 2+, X = (C 3H 7) 4N +(8); M = Pd 2+, X = (C 6H 13) 4N + (9); M = Pt 2+, X = (CH 3) 2NH 2 +(10); L = p-tolylsulfonyldithiocarbimate (CH 3C 6H 4SO 2NCS 2 2-)] have been prepared and characterized by elemental analysis, IR, 1H and 13C NMR and UV-Vis spectroscopy; 1, 3, 4 and 5 by X-ray crystallography. In 1, 3, 4 and 5, the Ni atom is four coordinate with a square planar environment being bonded to four sulfur atoms from two bidentate ligands. All the salts are weakly conducting (σ rt = 10 -7 to 10 -14 S cm -1) because of the lack of significant S···S intermolecular interactions between complex anions [M(L) 2] 2- in the solid state however, they show behavior of semiconductors in the temperature range 353-453 K. All the Pd(II) and Pt(II) salts exhibited phtotolumeniscent emissions near visible region in solution at room temperature. © 2011 Elsevier B.V. All rights reserved.
Preparation, characterization, and conducting properties of chalcogenocyanato based complex bimetallic salts and their I 2-doped products
(2012) Kiran Diwan; Nanhai Singh
Complex bimetallic salts of the form [M(bpy) 3][Co(NCX) 4] [M = Fe(II), X = S (1); M = Fe(II), X = Se (2); M = Fe(II), X = S, Se (3); M = Co(II), X = Se (4); M = Co(II), X = S, Se (5); M = Ni(II), X = S (6); M = Ni(II), X = Se (7); M = Ni(II), X = S, Se (8)] have been prepared and fully characterized various physicochemical techniques. Room temperature magnetic moments show significant antiferromagnetic coupling in the majority of complexes. Complexes 5-8 with σ rt ≈ 10 -8 Scm -1 are consistent with their behavior of semiconductor. © 2012 Copyright Taylor and Francis Group, LLC.
Supramolecular assemblies of metal ions in complex bimetallic and trimetallic salts based on hexacyanoferrate(III) ion
(Elsevier Ltd, 2010) Nanhai Singh; Kiran Diwan; Michael G.B. Drew
Two complex heterometallic salts with formulae Tl6[Fe(CN) 6]1.33(NO3)(OH) (1) and [Co(bpy) 2(CN)2]2{[Ag(CN)2] 0.5[Fe(CN)6]0.5}·8H2O (2) have been synthesized and fully characterized. Single crystal X-ray analyses reveal that compound 1 is comprised of discrete Tl+ cations and [Fe(CN)6]3- anions together with OH- and NO3- anions. Compound 2 contains [Co(bpy)2(CN)2]+ cations and {[Ag(CN)2][Fe(CN)6]}- anions together with eight molecules of water of crystallization. Both structures form unprecedented three-dimensional supramolecular networks via non-covalent interactions. Another important observation is that the stereochemically active inert (lone) pair present on Tl+ plays little role in controlling the structure of 1. The water molecules in 2 play important roles in providing stability, organizing a supramolecular network through hydrogen bonding. In the syntheses of 1 and 2, Fe(II) is oxidized to Fe(III) and Co(II) to Co(III), respectively, facilitating the formation of the salts that are obtained. Both compounds exhibit photoluminescence emission in solution near the visible region. © 2010 Elsevier Ltd. All rights reserved.
Syntheses and structural characterization of new heteroleptic 1,1′-bis(diphenylphosphino)ferrocene-dithio complexes of Ni, Pd and Pt: Their uses as sensitizers in TiO2 dye sensitized solar cells
(Elsevier B.V., 2013) Santosh K. Singh; Ratna Chauhan; Kiran Diwan; Michael G.B. Drew; Lal Bahadur; Nanhai Singh
A series of new heteroleptic complexes of the form [M(dppf)L] [where dppf = 1,1′-bis(diphenylphosphino)ferrocene; M = Ni(II) (1), Pd(II) (2), Pt(II) (3) and L = p-tolylsulfonyl dithiocarbimate, p-CH3C6H 4SO2NCS2; M = Ni(II) (4), Pd(II) (5), Pt(II) (6) and L = p-chlorobenzene sulfonyl dithiocarbimate, p-ClC6H 4SO2NCS2; M = Ni(II) (7), Pd(II) (8) and L = p-bromobenzene sulfonyl dithiocarbimate, p-BrC6H4SO 2NCS2; M = Ni(II) (9), Pd(II) (10) and L = 1-ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate (ecda), C2H 5OCO(CN)CCS2] have been synthesized and characterized by elemental analysis, spectroscopy (IR,1H, 13C and 31P NMR and UV-Vis.), cyclic voltammetry and single crystal X-ray diffraction and their light harvesting properties have been investigated by using them as photosensitizers in dye sensitized TiO2 solar cells. In these complexes the metal lies at the center of a distorted square planar environment; the distortion varies in the order Pd ≈ Pt > Ni. Among these, the nickel complexes showed light-to-electrical energy conversion efficiencies close to that shown by Ru dye N719 whereas the corresponding palladium and platinum complexes show inferior efficiencies under similar experimental conditions. © 2013 The Authors. Published by Elsevier B.V. All rights reserved.