2-Azabutadiene complexes of rhenium(): ,-chelated species with photophysical properties heavily governed by the ligand hidden traits

• Published in: Dalton transactions : an international journal of inorganic chemistry 2021-03, Vol.5 (8), p.2945-2963
• Main Authors: Schlachter, Adrien, Juvenal, Frank, Kinghat Tangou, Rodolphe, Khatyr, Abderrahim, Guyon, Fabrice, Karsenti, Paul-Ludovic, Strohmann, Carsten, Kubicki, Marek M, Rousselin, Yoann, Harvey, Pierre D, Knorr, Michael
• Format: Article
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d0dt04183a

The reaction of [Re(CO) 3 (THF)(μ-Br)] 2 or [Re(CO) 5 X] (X = Cl, Br, I) with the diaryl-2-azabutadienes [(RS) 2 C&z.dbd;C(H)-N&z.dbd;CAr 2 ] containing two thioether arms at the 4,4-position forms the luminescent S , N -chelate complexes fac -[(OC) 3 ReX{(RS) 2 C&z.dbd;C(H)-N&z.dbd;CAr 2 }] ( 1a-h ). The halide abstraction by silver triflate converts [(OC) 3 ReCl{(PhS) 2 C&z.dbd;C(H)-N&z.dbd;CPh 2 }] ( 1c ) to [(OC) 3 Re(OS(&z.dbd;O) 2 CF 3 ){(PhS) 2 C&z.dbd;C(H)-N&z.dbd;CPh 2 }] ( 1j ) bearing a covalently bound triflate ligand. The cyclic voltammograms reveal reversible S^N ligand-centred reduction and irreversible oxidation waves for all complexes. The crystal structures of nine octahedral complexes have been determined along with that of (NaphtylS) 2 C&z.dbd;C(H)-N&z.dbd;CPh 2 ( L6 ). A rich system of weak non-covalent intermolecular secondary interactions through CH X(Cl, Br)Re, CH O, CO π(Ph), CH πCO, CH O and CH S contacts has been evidenced. The photophysical properties have been investigated by steady-state and time-resolved absorption (fs transient absorption, fs-TAS) and emission (ns-TCSPC and ps-Streak camera) spectroscopy in 2-MeTHF solution at 298 and 77 K. The emission bands are composed of either singlet (450 < λ max < 535 nm) and/or triplet emissions (at 77 K only, λ max < 640 nm, or appearing as a tail at λ > 600 nm), which decay in a multiexponential manner for the fluorescence (short ps ( i.e.