Diradical character of neutral heteroleptic bis(1,2-dithiolene) metal complexes : case study of [Pd(Me2timdt)(mnt)] (Me2timdt = 1,3-dimethyl-2,4,5-trithioxoimidazolidine; mnt2– = 1,2-dicyano-1,2-ethylenedithiolate)
Abstract
The reaction of the bis(1,2-ditiolene) complex [Pd(Me2timdt)2] ( 1 ; Me2timdt•– = monoreduced 1,3-dimethyl-2,4,5-trithioxoimidazolidine) with Br2 yielded the complex [Pd(Me2timdt)Br2] ( 2 ), which was reacted with Na2mnt (mnt2– = 1,2-dicyano-1,2-ethylenedithiolate) to give the neutral mixed-ligand complex [Pd(Me2timdt)(mnt)] ( 3 ). Complex 3 shows an intense solvatochromic near-infrared (NIR) absorption band falling between 955 nm in DMF and 1060 nm in CHCl3 (ε = 10700 M–1 cm–1 in CHCl3). DFT calculations were used to elucidate the electronic structure of complex 3 , and to compare it with those of the corresponding homoleptic complexes 1 and [Pd(mnt)2] ( 4 ). An in-depth comparison of calculated and experimental structural and vis–NIR spectroscopic properties, supported by IEF-PCM TDDFT and NBO calculations, clearly points to a description of 3 as a dithione-dithiolato complex. For the first time, a Broken-Symmetry (BS) procedure for the evaluation of the singlet diradical character (DC) of heteroleptic bis(1,2-dithiolene) complexes has been developed and applied to complex 3 . The DC, predominant for 1 (nDC = 55.4%), provides a remarkable contribution to the electronic structures of the ground states of both 3 and 4, showing a diradicaloid nature (nDC = 24.9% and 27.5%, respectively). The computational approach developed here clearly shows that a rational design of the DC of bis(1,2-ditiolene) metal complexes, and hence their linear and nonlinear optical properties, can be achieved by a proper choice of the 1,2-dithiolene ligands based on their electronic structure.
Citation
Aragoni , M C , Caltagirone , C , Lippolis , V , Podda , E , Slawin , A M Z , Woollins , J D , Pintus , A & Arca , M 2020 , ' Diradical character of neutral heteroleptic bis(1,2-dithiolene) metal complexes : case study of [Pd(Me 2 timdt)(mnt)] (Me 2 timdt = 1,3-dimethyl-2,4,5-trithioxoimidazolidine; mnt 2– = 1,2-dicyano-1,2-ethylenedithiolate) ' , Inorganic Chemistry , vol. Articles ASAP . https://doi.org/10.1021/acs.inorgchem.0c02696
Publication
Inorganic Chemistry
Status
Peer reviewed
ISSN
0020-1669Type
Journal article
Description
M. A., M. C. A., C. C., and V. L. thank the Fondazione di Sardegna (FdS) and Regione Autonoma della Sardegna (RAS) (Progetti Biennali di Ateneo FdS/RAS annualità 2018) for financial support. A.P. acknowledges RAS for the funding in the context of the POR FSE 2014−2020 (CUP F24J17000190009).Collections
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