The reaction of [Pt(C^N)(CFCO)(SMe)] (1), in which C^N is either benzo[ h]quinolinate (bhq), 1a, or 2-phenylpyridinate (ppy), 1b, with 1 equiv of bis(diphenylphosphino)methane (dppm) gave the bischelate complexes [Pt(C^N)dppm]CFCO (2). The binuclear complexes [Pt(C^N)(CFCO)(μ-dppm)] (3) were prepared, using an unusual reaction pathway, by the addition of equimolar amount of complexes 1 and 2, through the ring opening of the chelating dppm ligand and coordination of the CFCO anion to the platinum center. The proposed reaction pathway and effect of the solvent polarity were investigated by density functional theory (DFT) calculations. The crystal structure of 3a shows considerable intramolecular Pt···Pt and π···π interactions. The crystal structure and formation pathway toward 3 were compared with the similar analogue [Pt(bhq)(Cl)(μ-dppm)] (5). All complexes were fully characterized using multinuclear NMR spectroscopy and elemental analysis. Furthermore, the crystal structures of some complexes including 1b, 2a, 2b, 3a, and 5 were confirmed by X-ray crystallography. The effect of dimerization via a change in the coordination mode of dppm, from a chelate mode in complex 2 to a bridge mode in complexes 3 and 5, upon the excited states of the studied compounds was investigated in their distinguished absorption and emission profiles. The appearance of a remarkably low energy band in the absorption spectra of 3, which was assigned to a metal-metal to ligand charge transfer [MMLCT; dσ*(Pt) → π*(C^N)] transition showing negative solvatochromism, is important evidence for the Pt···Pt intramolecular interaction. The vibronically resolved and long-lifetime emission of 2a in poly(methyl methacrylate) media and powder states at 77 and 300 K, along with time-dependent DFT calculations, suggested that the triplet ligand-centered (LC) emission was mixed with some MLCT character. Unstructured and short-lifetime emission in 3 refers to the phosphorescenceMMLCT [dσ*(Pt) → π*(C^N)] transition. Although complex 5 is a binuclear compound, the long distance of the Pt···Pt interaction caused the occurrence of the MMLCT transition to fade and act as a mononuclear unit, and the emission originated mostly from theMLCT transition. As a result, more metal participation leads to more red-shifted absorption and emission spectra of the studied complexes upon going from LC to MLCT to MMLCT transitions (λ and λ: 3a > 3b > 5 > 2a > 2b).

By the reactions of bis(diphenylphosphino)amine (dppa) with equimolar amounts of cycloplatinated(II) complexes 1 with two neutral (SMe 2 or DMSO) and anionic (Cl − or CF 3 CO 2 − ) labile ligands the bis-chelate complexes 2 with a chelating mode of dppa were synthesized that have one of the smallest bite angles in a diphosphine. As the usual strategy for synthesizing the binuclear complexes, the reactions of 0.5 equiv of dppa with cycloplatinated(II) complexes 1 with a Cl − ligand were successful in making symmetrical binuclear complexes. Also, the chelating dppa has a strong angle strain that makes it a susceptible precursor for biphosphine ring opening. Furthermore, this new strategy was successful for designing symmetrical and unsymmetrical binuclear complexes with Cl − ligands. Interestingly, all efforts to make binuclear complexes with bridging dppa from precursors that contain CF 3 CO 2 − were unsuccessful by both strategies. The effects of dimerization via a change in the coordination mode of dppa, from a chelate mode in complexes 2 with green emission to a bridge mode in complexes 3, with dualphosphorescence red emission were investigated in the powder and poly(methyl methacrylate) (PMMA) phases at 77 and 298 K. The emission decay curves of all complexes in the solid state show long and short lifetime values as characteristics of the triplet excited states. The reaction pathway, reactivity, and structural aspects of the complexes were compared with those of other similar dppm analogues and the mechanism of conversion via possible intermediates was considered by density functional theory (DFT) calculations. For interpretation of the emission spectra, time-dependent DFT (TD-DFT) calculations were carried out on the isolated and stacked forms.