Nitrile substituents at the conjugated dipyridophenazine moiety as infra-red redox markers in electrochemically reduced heteroleptic Ru(II) polypyridyl complexesSumner, E., Pižl, M., McQuaid, K. T. ORCID: https://orcid.org/0000-0002-3222-5584 and Hartl, F. ORCID: https://orcid.org/0000-0002-7013-5360 (2024) Nitrile substituents at the conjugated dipyridophenazine moiety as infra-red redox markers in electrochemically reduced heteroleptic Ru(II) polypyridyl complexes. Inorganic Chemistry, 63 (5). pp. 2460-2469. ISSN 0020-1669
It is advisable to refer to the publisher's version if you intend to cite from this work. See Guidance on citing. To link to this item DOI: 10.1021/acs.inorgchem.3c03484 Abstract/SummaryRuthenium(II) complexes [Ru(tap)2(NN)]2+ (tap = 1,4,5,8-tetraazaphenanthrene, NN = 11-cyano-dipyrido[3,2-a:2’,3’-c]phenazine (11-CN-dppz) and 11,12-dicyano-dipyrido[3,2-a:2’,3’-c]phenazine (11,12-CN-dppz)) feature the C≡N groups as IR-active redox markers. They were studied by cyclic voltammetry, UV-Vis and IR spectroelectrochemistry (SEC), and DFT calculations to assign the four 1e– reduction waves R1–R4 observed in dichloromethane. Generally, the NN ligands are reduced first (R1). For [Ru(tap)2(11,12-CN-dppz)]2+, R1 is sufficiently separated from R2 delocalized over both tap ligands. Accordingly, IR SEC conducted at R1 shows a large red shift of the s,as(CN) modes by –18/–28 cm–1, accompanied by 4-fold enhancement of the s(CN) intensity, comparably with reference data for free 11,12-CN-dppz. The first tap-based reduction of spin-doublet [Ru(tap)2(11,12-CN-dppz)]+ to spin-triplet [Ru(tap)2(11,12-CN-dppz)] at R2 decreased (CN) by mere –2 cm–1 whilst the intensity enhancement reached an overall factor of 8. Comparably, a red shift of (CN) by –27 cm–1 resulted from the 1e– reduction of [Ru(tap)2(11-CN-dppz)]2+ at R1 (poorly resolved from R2) and the intensity enhancement was roughly 3-fold. Concomitant 1e– reductions of the tap ligands (R2 and R3) caused only minor (CN) shifts of –3 cm–1 and increased the absorbance by an overall factor of 6.5 and 8, respectively.
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