In the present work we obtained a series of NIR luminescent platinum(II) complexes with a pincer N^N^C ligand based on the conjugated {benzoimidazo[1,2-a]pyrazine} system with the [Pt(N^N^C)L]n+ structural motif (L = phosphine, alkynyl or pyridine-type ligands). We have also synthesized two complexes with bidentate phosphines that demonstrate different types of coordination: 1) as chelating ligand (in case of 1,2-bis(diphenylphosphino)benzene), that led to de-coordination of pyridine ring of N^N^C ligand and formation of a [Pt(N^C)dppb]+ complex; 2) as a bridging ligand (in case of bis(diphenylphosphino)methane) between two {Pt(N^N^C)} fragments in a dimeric complex of type [{Pt(N^N^C)}2dppm]2+. The complexes obtained were fully characterized using spectroscopic methods, and their ground-state structures and photophysical properties were studied by DFT and TD DFT methods. According to the data obtained the aromatic {benzoimidazo[1,2-a]pyrazine} fragment plays a key role in the photophysics of this type of complexes and the triplet 3LC state located at the N^N^C ligand proved to be the only emissive state in all the complexes prepared. Unexpectedly variations in the nature of the ligands occupying the fourth coordination position in the square-planar structural motif, changes in the mode of the N^N^C ligand coordination and even the Pt-Pt bond formation did not result in significant variations of the emission profile. The photophysical behavior of these complexes has been analyzed using DFT calculations, which are in complete agreement with the experimental data and confirmed that the lowest relaxed triplet configuration responsible for the phosphorescence in the complexes studied is located at the N^N^C ligand.
Original languageEnglish
Article number119776
JournalInorganica Chimica Acta
Early online date27 May 2020
Publication statusPublished - Oct 2020

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