Synthesis and properties of [Pt(4-CO(2)CH(3)-py)(2)(mnt)]: comparison of pyridyl and bipyridyl-based dyes for solar cells.

The dye complexes [Pt(4-CO(2)R-py)(2)(mnt)] (R = H (3a), CH(3) (3b)) and the precursor complexes [Pt(4-CO(2)R-py)(2)Cl(2)] (2a, 2b) (py = pyridyl) were synthesised, characterised by electrochemical, spectroscopic, spectroelectrochemical (UV-vis-nIR and in situ EPR) and hybrid DFT computational methods and attached to a TiO(2) substrate to determine charge recombination kinetics. The results were compared to the bipyridyl analogues [Pt{X,X'-(CO(2)R)-2,2'-bipyridyl}(mnt)], (X = 3 or 4). The electronic characteristics of the bis-pyridyl complex were found to be different to the bipyridyl complexes making the former harder to reduce, shifting the lowest-energy absorption band to higher energy and showing separate degenerate LUMO orbitals on the two pyridine rings. The latter point determines that the di-reduced pyridyl complex remains EPR active, unlike the bipyridyl analogue. Complex 3a attached to nanocrystalline TiO(2) shows a long charge recombination lifetime in comparison with the analogous complex with the ubiquitous 4,4'-(CO(2)H)(2)-bipyridyl ligand, suggesting that pyridyl complexes may possess some advantage over bipyridyl complexes in dye-sensitised solar cells.

Sensitized near-infrared emission from complexes of YbIII, NdIII and ErIII by energy-transfer from covalently attached PtII-based antenna units.

A series of dinuclear platinum(II)-lanthanide(iii) complexes has been prepared in which a square-planar Pt(II) unit, either [(PPh(3))(2)Pt(pdo)] (H(2)pdo=5,6-dihydroxyphenanthroline) or [Cl(2)Pt(dppz)] [dppz=2,3-bis(2-pyridyl)pyrazine], is connected to a Ln(dik)(3) unit ("dik"=a 1,3-diketonate ligand). The mononuclear complexes [(PPh(3))(2)Pt(pdo)] and [Cl(2)Pt(dppz)] both have external, vacant N,N-donor diimine-type binding sites that react with various [Ln(dik)(3)(H(2)O)(2)] units to give complexes [(PPh(3))(2)Pt(micro-pdo)Ln(tta)(3)] (series A; Htta=thenoyltrifluoroacetone), [Cl(2)Pt(micro-dppz)Ln(tta)(3)] (series B); and [Cl(2)Pt(micro-dppz)Ln(btfa)(3)] (series C; Hbtfa=benzoyltrifluoroacetone); in all of these the lanthanide centres are eight-coordinate. The lanthanides used exhibit near-infrared luminescence (Nd, Yb, Er). Crystal structures of members of each series are described. In all complexes, excitation into the Pt-centred absorption band (at 520 nm for series A complexes; 440 nm for series B and C complexes) results in characteristic near-IR luminescence from the Nd, Yb or Er centres in both the solid state and in CH(2)Cl(2), following energy-transfer from the Pt antenna chromophore. This work demonstrates how d-block-derived chromophores, with their intense and tunable electronic transitions, can be used as sensitisers to achieve near-infrared luminescence from lanthanides in suitably designed heterodinuclear complexes based on simple bridging ligands.

Sensitised near-infrared emission from lanthanides using a covalently-attached Pt(II) fragment as an antenna group.

In a series of heterodinuclear complexes in which a Pt(PPh3)2(catecholate) chromophore is covalently linked to a lanthanide tris(diketonate) unit, sensitised near-IR emission from Yb(III), Nd(III) and Er(III) occurs on excitation of the Pt(II) chromophore at 520 nm.