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Issue 31, 2006
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A new family of luminescent compounds: platinum(II) imidoylamidinates exhibiting pH-dependent room temperature luminescence

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Abstract

The imidoylamidinate platinum(II) compounds [Pt{NH[double bond, length as m-dash]C(R)NC(Ph)[double bond, length as m-dash]NPh}2] (R = CH2Ph 2, p-ClC6H43, Ph 4) were prepared by the reaction of the appropriate trans-[PtCl2(RCN)2] with 4 equiv of the amidine PhC([double bond, length as m-dash]NH)NHPh giving 2–4 and 2 equivs of the salt PhC([double bond, length as m-dash]NH)NHPh·HCl. We also synthesized, by the double alkylation of 4 with MeOSO2CF3, complex [Pt{NH[double bond, length as m-dash]C(Ph)N(Me)C(Ph)[double bond, length as m-dash]NPh}2][CF3SO3]2 (5) which models the bis-protonated form of 4. The complexes were characterized by 1H, 13C NMR, and IR spectroscopies, FAB-MS and by C, H, N elemental analysis. The X-ray crystallography of 4·2CH2Cl2 enables the confirmation of the square planar coordination geometry of the metal center with almost planar imidoylamidine ligands, while in 5·2CHCl3 the planarity of the metallacycles is lost and and the central N atom is sp3-hybridized. The imidoylamidinate complexes represent a new family of Pt(II)-based luminescent complexes and they are emissive at room temperature both in solution and in the solid state, with an emission quantum yield ranging from 3.7 × 10−4 to 6.2 × 10−2 in methanol solution; the emission intensity is pH-dependent, being quenched at low pH. UV-visible and luminescence spectroscopies indicate that the lowest excited state of these compounds is 3MLCT or 3IL with significant MLCT character, with emission lifetimes of a few µs. A blue shift of both the absorption and emission with increasing solvent polarity and with decreasing π-electron withdrawing properties of the ligand substituent was observed.

Graphical abstract: A new family of luminescent compounds: platinum(ii) imidoylamidinates exhibiting pH-dependent room temperature luminescence

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Publication details

The article was received on 13 Feb 2006, accepted on 10 Apr 2006 and first published on 08 May 2006


Article type: Paper
DOI: 10.1039/B602083F
Citation: Dalton Trans., 2006, 3798-3805
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    A new family of luminescent compounds: platinum(II) imidoylamidinates exhibiting pH-dependent room temperature luminescence

    G. H. Sarova, N. A. Bokach, A. A. Fedorov, M. N. Berberan-Santos, V. Yu. Kukushkin, M. Haukka, J. J. R. Fraústo da Silva and A. J. L. Pombeiro, Dalton Trans., 2006, 3798
    DOI: 10.1039/B602083F

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