pH-Dependent Spectroscopic and Luminescent Properties, and Metal-Ion Recognition Studies of Re(I) Complexes Containing 2-(2′-Pyridyl)benzimidazole and 2-(2′-Pyridyl)benzimidazolate

A series of Re(I) complexes, [Re(CO)(3)Cl(HPB)] (1), [Re(CO)(3)(PB)H2O] (2), [Re(CO)(3)(NO3)(PB-AuPPh3)] (3), and (Re(CO)(3)(NO3)(PB)Au(dppm-H)Auk (4) [HPB = 2-(2'-pyridyl)benzirnidazole; dppm = 2,2'-bis(diphenylphosphinomethane)], have been synthesized and characterized by X-ray diffraction. Complex 1, which exhibits interesting pH-dependent spectroscopic and luminescent properties, was prepared by reacting Re(CO)(5)Cl with an equimolar amount of 2-(2'-pyridyl)benzimidazole. The imidazole unit in complex 1 can be deprotonated to form the imidazolate unit to give complex 2. Addition of 1 equiv of AuPPh3(NO3) to complex 2 led to the formation of a heteronuclear complex 3. Addition of a half an equivalent of dppm(Au(NO3))2 to complex 2 yielded 4. In both 3 and 4, the irnidazolate unit acts as a multinuclear bridging ligand. Complex 4 is a rare and remarkable example of a Re2Au4 aggregate in combination with mu(3)-bridging 2-(2'-pyridyl)benzimidazolate. Finally, complex 2 has been used to examine the Hg2+- recognition event among group 12 metal ions. Its reversibility and selectivity toward Hg2+ are also examined.