We thank Professor G. R. Desiraju for suggesting crystallization of pyridine-d¬5¬, and STFC for provision of neutron beam-time and a studentship for SC. RB gratefully acknowledges the support of the DFG FOR 618. [ † ] We dedicate this paper to Dr Frank Allen on the occasion of his retirement as Executive Director of the Cambridge Crystallographic Data Centre.
Supporting information:Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Crystallographic information files can be obtained from the Cambridge Crystallographic Data Centre, quoting deposition numbers CCDC 695956 -695959. A summary table of crystal data is also given in the Supporting Information.
We report the preparation and electrochemical studies of a systematic series of mono- and di-nitro-substituted 2,2'-bipyridine (bipy) compounds [x-NO(2)-bipy (x = 3,4) and x,x'-(NO(2))(2)-bipy (x,x' = 3, 4, 5)] and their complexes with platinum(II), [Pt(x-NO(2)-bipy)Cl(2)] and [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)]. The effect of the number and substitution pattern of the nitro groups on the low-lying acceptor molecular orbitals (involved in charge transfer transitions) is probed by in situ UV/Vis/NIR and EPR spectroelectrochemical methods, supported by DFT calculations. The LUMOs of x-NO(2)-bipy (x = 3-5) are largely localised on the NO(2)-pyridyl moiety; this is also true of their {PtCl(2)} complexes but with a small but significant shift of electron density from the nitro groups. The LUMOs of x,x'-(NO(2))(2)-bipy with x = 3 and 5 are delocalised over both NO(2)-pyridyl rings, but for 4,4'-(NO(2))(2)-bipy is localised on a single NO(2)-pyridyl ring. In all cases the LUMO of the [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)] complexes is delocalised over both nitro-pyridyl rings. For all complexes, the 4(4') derivatives allows greatest overlap with metal valence orbitals in the LUMO.
We thank Professor G. R. Desiraju for suggesting crystallization of pyridine-d¬5¬, and STFC for provision of neutron beam-time and a studentship for SC. RB gratefully acknowledges the support of the DFG FOR 618. [ † ] We dedicate this paper to Dr Frank Allen on the occasion of his retirement as Executive Director of the Cambridge Crystallographic Data Centre.
Supporting information:Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Crystallographic information files can be obtained from the Cambridge Crystallographic Data Centre, quoting deposition numbers CCDC 695956 -695959. A summary table of crystal data is also given in the Supporting Information.
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