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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