Reduced and Excited States of (bpym)[PtCl₂]<i>_n</i> (bpym = 2,2‘-Bipyrimidine; <i>n</i> = 1, 2): Experiments and DFT Calculations

The complexes (bpym)PtCl2 (1) and the new (μ-bpym)[PtCl2]2 (2), bpym = 2,2‘-bipyrimidine, were synthesized and, in the case of 1, crystallized in solvent-free form for X-ray diffraction. The molecules 1 exhibit two different kinds of stacking motifs in the crystal with an interstack CH--N interaction. Complexes 1 and 2 were found to be sufficiently soluble for cyclic voltammetry, spectroscopy (absorption and emission), and spectroelectrochemical studies (UV−vis, EPR). As a result of single or double coordination of the strongly σ-accepting [PtCl2] fragment to bpym, the paramagnetic anions 1•- and 2•- and the dianions 12- and 22- could be reversibly generated, despite the presence of metal−halide bonds. DFT calculations of A(195Pt) and g tensor components confirm that the singly occupied MOs of the monoanionic species have mainly π*(bpym) character with nonnegligible platinum d orbital participation. The assignments of the electronic absorption and emission and resonance Raman spectra for both complexes are supported by DFT calculations.