Targeting divalent metal cations with Re(i) tetrazolato complexesElectronic supplementary information (ESI) available: X-ray crystallographic data for the complexes fac-[Re(bipy)(CO)3(2-PTZ)], fac-[Re(phen)(CO)3(2-PTZ)], fac-[Re(phen)(CO)3(2-QTZ)], [Re-(2-PTZ)-Cu]+, [Re-(2-QTZ)-Cu] in CIF format. IR and NMR (1H, 13C) spectra of all the Re(i) based species. UV-vis absorption, emission spectra recorded at r.t. and at 77 K, emission titrations, Stern-Volmer plots. CCDC 1422231-1422235. For ESI and

• Main Authors: Fiorini, Valentina, Ranieri, Anna Maria, Muzzioli, Sara, Magee, Karen D. M, Zacchini, Stefano, Akabar, Nurshadrina, Stefan, Alessandra, Ogden, Mark I, Massi, Massimiliano, Stagni, Stefano
• Format: Journal Article
• Language: English
• Published: 24.11.2015
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt03690a

In order to exploit their potential as versatile luminescent sensors, four new Re( i )-tetrazolato complexes with the general formula fac -[Re(CO) 3 ( diim )( L )], where diim is 2,2′-bipyridine ( bipy ) or 1,10-phenanthroline ( phen ) and L − is either the anion 5-(2′-pyridyl)tetrazolato ( 2-PTZ − ) or 5-(2′-quinolyl)tetrazolato ( 2-QTZ − ), were prepared and fully characterized. In all cases, the regioselective coordination of the Re( i ) center through the N2 atom of the tetrazolato ring was observed. This particular feature ensures the availability of the diiminic ( N^N ) site that was systematically incorporated into the structure of the 2-PTZ − and 2-QTZ − ligands for further coordination with metal cations. Such a diimine-type coordination mode was preliminarily tested by using the mononuclear Re( i ) complexes as N^N ligands for the preparation of two [( N^N )Cu( POP )] cationic species, where POP is the chelating diphosphine bis[2-(diphenylphosphino)phenyl]ether. The X-ray structures of the resulting Re( i )-Cu( i ) dyads revealed that the Re( i ) mononuclear complexes effectively behaved as chelating N^N ligands with respect to the [Cu( POP )] + fragment, the coordination of which also resulted in significant modification of the Re( i )-centered luminescence. With these data in hand, the luminescent sensing abilities of the four new Re( i ) tetrazolato complexes were screened with respect to divalent metal ions of toxicological and biological importance such as Zn( ii ), Cd( ii ) and Cu( ii ). The interaction of the Re( i ) complexes with Zn( ii ) and Cd( ii ) was witnessed by the evident blue shift (Δ λ max = 22-36 nm) of the emission maxima, which was also accompanied by a significant elongation of the emission lifetimes. On the contrary, the addition of the cupric ion caused substantial quenching of the radiative processes originating from the Re( i ) luminophores. The design, preparation and characterization of four new Re( i ) tetrazolato complexes together with the study of their luminescent sensing abilities toward Zn( ii ), Cd( ii ) and Cu( ii ) are described herein.