Influence of the 4‐Substituted Pyridine Ligand L′ on both the Conformation and Spectroscopic Properties of the (2,2′‐Biquinoline‐ κN 1 , κN 1 ′)tricarbonyl(pyridine‐ κN 1 )rhenium(1+) Complex ([Re(CO) 3 ‐(bqui)(py)] + ) and Its Derivatives [Re(CO) 3 (L)(L′)] + (L = 2,2′‐Biquinoline and 3,3′‐(Ethane‐1,2‐diyl)‐2,2′‐biquinoline)

A series of new rhenium(I) complexes of the type [Re I (CO) 3 (L)(L′)] n + (L = 2,2′‐biquinoline (bqui) or 3,3′‐(ethane‐1,2‐diyl)‐2,2′‐biquinoline (CH 2 CN 2 )bqui); L′ = CF 3 SO $\rm{_3^ - }$ , pyridine (py), or 4‐substituted pyridine (HOpy, Bzpy, or NCpy); n  = 0 or 1) were prepared and characterized by FT‐IR, 1 H‐NMR, UV/VIS and emission spectroscopy, luminescence lifetimes, and cyclic voltammetry. The pseudo‐octahedral facial configuration was established by X‐ray single‐crystal diffraction analysis of two complexes and by a FT‐IR study of all complexes. The [Re(CO) 3 (bqui)(Bzpy)](CF 3 SO 3 ) complex crystallizes in the form of two mirror isomers arising from the conformational mobility of the biquinoline ligand. A correlation between the metal‐to‐ligand charge‐transfer (MLCT) emission maxima and the σ + Hammett parameter was established for the complexes of the bqui series, while such correlation was not observed for the complexes of the (CH 2 CH 2 )bqui series. No correlation between oxidation potentials and the Hammett parameters was established. The results were rationalized in function of the effect of the 4‐substituted pyridine ligand on the octahedral distortion and conformational characteristic of the complexes. The 1 H‐NMR data confirmed these results.