Diimine ligand structure effects on photophysical properties of tricarbonyl rhenium(I) complexes having arylborane charge transfer units

•Structure–property relationships of rhenium(I)–arylborane complexes (ReB) were discussed.•ReB showed broad and intense absorption irrespective of the ligand structure.•ReB showed low-energy and long-lived emission irrespective of the ligand structure.•More effective MLCT/π(aryl)-p(B) CT interactions were for the phen-type complex.•Substitution position effects were studied based on DFT calculations.

We report the synthesis and photophysical properties of a novel tricarbonyl rhenium(I) complex having a (dimesityl)boryldurylethynyl (DBDE) group at the 4-position of a 2,2′-bipyridine (bpy) ligand, fac-[Re(CO)3(DBDE-bpy)Br] = ReBbpy, and discuss the diimine ligand structure effects on the spectroscopic and photophysical properties of the complex by comparing with those of the relevant 4-DBDE-1,10-phenanthroline (phen) type complex: fac-[Re(CO)3(DBDE-phen)Br] = ReBphen. The present study demonstrated that ReBbpy showed smaller DBDE effects on the spectroscopic and photophysical properties compared with ReBphen, whose origin was discussed in terms of the redox, absorption/emission, and time-dependent density functional theory calculation data on the complexes.

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