Syntheses, structures and photoluminescent properties of silver(I) complexes with in situ generated hexahydropyrimidine derivatives

Abstract

Two new linear and V-shaped tetradentate ligands, namely 1,4-bis(2-hexahydropyrimidyl)benzene (L) and 1,3-bis(2-hexahydropyrimidyl)benzene (L ′), and their silver(I) complexes, [Ag 2L(μ-ONO 2)](NO 3) · 2H 2O ( 1), [Ag 2L(μ-pn)](NO 3) 2 ( 2), [Ag 2L(μ-pn)](ClO 4) 2 ( 3) and [Ag 4L ′ 2(H 2O)](NO 3) 4 · 5H 2O ( 4) (pn=1,3-diaminopropane) have been synthesized in situ and structurally characterized by single-crystal X-ray diffraction. 1 and 2 were obtained from the same reaction solution but different crystallization conditions. 1 is an one-dimensional chain featuring cuboid tetranuclear silver(I) units interconnected through monoatomic nitrate bridges. Both 2 and 3 are ribbon-like helical compounds in which each L ligand acts in a tetradentate bridging mode to interconnect four metal atoms, and each pn ligand functions in a bidentate bridging mode to link a pair of metal atoms. 4 shows a truncated square-pyramidal tetranuclear motif arose by the V-shaped L ′ ligand. Close Ag⋯Ag separations (2.901–2.939 Å) assisted by bis(hexahydropyrimidine) bridges were observed in 1 and 4, indicating metal–metal interactions. Photoluminescence of 1– 4 has also been observed in the solid state and solution at room temperature and low temperature, respectively.