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Abstract
Dinuclear complexes bearing Ru(II) photoactive center are of interest for the development of efficient dual catalysts for many photocatalyzed reactions. Ditopic polypyrine ligands – bis(pyridine-2-yl)amino-1,10-phenanthrolines – containing additional coordination site (bis(pyridine-2-yl)amine, dpa) at positions 3, 4 or 5 of 1,10-phenanthroline core (Phen-3NPy2, Phen-4NPy2 and Phen-5NPy2) were synthesized. They were used as bridging ligands to obtain dinuclear complexes of composition [(bpy)2Ru(Phen-NPy2)PdCl2](PF6)2 (Ru(Phen-NPy2)Pd) via stepvise comlexing in good yields. Ru(II) is coordinated to 1,10-phenanthroline in these complexes, while Pd(II) is bound to dpa chelating moiety, which was established by NMR spectroscopy and X-ray single crystal analysis. The influence of the position of dpa in phenanthroline ring on the structural, optical and electrochemical properties of Ru(Phen-NPy2)Pd complexes was studied. The complexes possess photoluminescence in argon-saturated MeCN solution with maxima in the range of 615–625 nm, emission quantum yields range from 0.11 to 0.15 for Ru(Phen-NPy2) complexes and from 0.018 to 0.026 for dinucear Ru(Phen-NPy2)Pd complexes. All the complexes have high extinction coefficients in the range of 370–470 nm, efficiently absorb visible light and can be used as photocatalysts. The Ru2+/3+ potential in Ru(Phen-NPy2)Pd complexes showed no significant dependence on dpa position, while Pd2+/0 reduction potential was quite lower for Ru(Phen-3NPy2)Pd and Ru(Phen-NPy2)Pd, than for Ru(Phen-NPy2)Pd (–0.57V and –0.72V vs Ag/AgCl, KCl(sat), respectively). The behaviour of the complexes was studied in Сu-free Sonogashira coupling under blue LED (12 W) irradiation. The reaction proceeds three times faster when Ru(Phen-4NPy2)Pd and Ru(Phen-3NPy2)Pd are used as catalysts precursors than in the case of mixed catalytic system Ru(bpy)3(PF6)2/(RNPy2)PdCl2.
Supplementary materials
Title
Supporting information
Description
General information on materials, methods and synthesis of ligands and complexes, UV–vis spectra, NMR spectra and mass for the synthesized compounds, additional data on X-ray structures, electrochemistry, photocatalysis and DFT calculations.
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