Abstract
Five d(10) transition-metal clusters, {[Zn-rs(2,6-Hbptp)(2,6-bptp)(7)(mu(2)-O)(4)(mu(2)-OH)(4)(HCOO)(2)(NO3)(H2O)(2)]center dot 20H(2)O} (1), {[Zn-8(2,6-Hbptp)(2,6-bptp)5(mu(3)-O)(2)]center dot(ClO4)center dot 7H(2)O} (2), {[Cd-8(2,6-Hbptp)(2)(2,6-bptp)(4)(mu(3)-O)(2)]center dot(NO3)(2)center dot 10H(2)O} (3), {[Ag-7(2,6-Hbptp)(2,6-bptp)(3)]center dot 4H(2)O center dot CH3OH}(n) (4), and {[Ag-6(2,6-Hbptp)(2)(2,6-bptp)(2)][Ag-6(2,6-Hbptp)(2)(2,6-bptp)(2)](2)center dot 30H(2)O center dot 4CH(3)OH} (5), based on bent ligand 2,6-bis[3-(pyrazin-2-yl)-1,2,4-triazolyl]pyridine (2,6-H(2)bptp) have been synthesized. Compound 1 exhibits a novel fanlike Zn15 cluster, which is the highest-nuclearity Zn cluster with 2,6-H2bptp reported thus far. In 2 or 3 (M = Zn/Cd), each ligand coordinates to three M2+ ions, to form an M8L6 cluster. The structure of compound 4 is a Ag-6 cluster-based 1D chain, where each hexanuclear [Ag-6(2,6-Hbptp)(2,6-bptp)(3)](-) cluster links its equivalent ones via sharing the Ag atom. Compound 5 contains two kinds of Ag-6 clusters, and the alternating arrangement of them gives the final structure. It is worth mentioning that the AgAg bond distances in 4 and 5 are relatively very short and suggest a closed-shell d(10)-d(10) argentophilic interaction. The luminescence properties of compounds 15 have been researched at ambient and low temperatures. Interestingly, the emission intensities of 15 increase gradually upon cooling. A new strong emission band for 4 appears at 610 nm exhibiting red-orange luminescence. The low-energy emissions (620 nm) of 5 gradually blue shift to shorter wavelengths.