New members of the [Ru(diimine)(CN)(4)](2-) family: structural, electrochemical and photophysical properties

Adams, H., Alsindi, W. Z., Davies, G. M., Duriska, M. B., Easun, Timothy ORCID: https://orcid.org/0000-0002-0713-2642, Fenton, H. E., Herrera, J. M., George, M. W., Ronayne, K. L., Sun, X. Z., Towrie, M. and Ward, M. D. 2006. New members of the [Ru(diimine)(CN)(4)](2-) family: structural, electrochemical and photophysical properties. Dalton Transactions (1) , pp. 39-50. 10.1039/B509042C

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Abstract

A series of complexes of the type K2[Ru(NN)(CN)4] has been prepared, in which NN is a diimine ligand, and were investigated for both their structural and photophysical properties. The ligands used (and the abbreviations for the resulting complexes) are 3-(2-pyridyl)pyrazole (Ru-pypz), 2,2′-bipyrimidine (Ru-bpym), 5,5′-dimethyl-2,2′-bipyridine (Ru-dmb), 1-ethyl-2-(2-pyridyl)benzimidazole (Ru-pbe), bidentate 2,2′:6′,2[triple prime]-terpyridine (Ru-tpy). The known complexes with NN = 2,2′-bipyridine (Ru-bpy) and 1,10-phenathroline (Ru-phen) were also included in this work. A series of crystallographic studies showed that the [Ru(NN)(CN)4]2− complex anions form a range of elaborate coordination networks when crystallised with either K+ or Ln3+ cations. The K+ salts are characterised by a combination of near-linear Ru–CN–K bridges, with the cyanides coordinating to K+ in the usual ‘end-on’ mode, and unusual side-on π-type coordination of cyanide ligands to K+ ions. With Ln3+ cations in contrast only Ru–CN–Ln near-linear bridges occurred, affording 1-dimensional helical or diamondoid chains, and 2-dimensional sheets constituted from linked metallamacrocyclic rings. All of the K2[Ru(NN)(CN)4] complexes show a reversible Ru(II)/Ru(III) couple (ca. +0.9 V vs. Ag/AgCl in water), the exception being Ru-tpy whose oxidation is completely irreversible. Luminescence studies in water showed the presence of 3MLCT-based emission in all cases apart from Ru-bpym with lifetimes of tens/hundreds of nanoseconds. Time-resolved infrared studies showed that in the 3MLCT excited state the principal C–N stretching vibration shifts to positive energy by ca. 50 cm−1 as a consequence of the transient oxidation of the metal centre to Ru(III) and the reduction in back-bonding to the cyanide ligands; measurement of transient decay rates allowed measurements of 3MLCT lifetimes for those complexes which could not be characterised by luminescence spectroscopy. A few complexes were also examined in different solvents (MeCN, dmf) and showed much weaker emission and shorter excited-state lifetimes in these solvents compared to water.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	Royal Society of Chemistry
Last Modified:	28 Oct 2022 08:30
URI:	https://orca.cardiff.ac.uk/id/eprint/71031

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