Synthesis and structural characterization of Bis(mu(2)-aqua)tetrakis(aqua)dilithium(i) Bis(4-nitrobenzoate)

Abstract

Reaction of alkali metal carbonates M2CO3 (M = Li or Na) with 4-nitrobenzoic acid (4-nbaH) results in the formation of [(H2O)(4)Li-2(mu-H2O)(2)](4-nba)(2) (4-nba = 4-nitrobenzoate) (1) and [Na(4-nba)(H2O)(3)] (2). Compounds (1) and (2) have been characterized by analytical, spectral and thermal data. The structure of (1) consists of bis(mu(2)-aqua)tetrakis(aqua)dilithium(I) dication situated on an inversion centre and a free 4-nba anion. In compound (2), one of the two independent 4-nba functions as a mu(2)-bridging bidentate ligand, bridging the two unique Na(I) ions via the oxygen atoms of the nitro functionality. Hydrogen bonding of coordinated water ligands in a dinuclear lithium cation with coordinated water molecules in an adjacent unit leads to the formation of a supramolecular chain of [(H2O)(4)Li-2(mu-H2O)(2)](2+) cations. The cationic chain is further H-bonded to 4-nba anions resulting in alternating layers of [(H2O)(4)Li-2(mu-H2O)(2)](2+) cations and 4-nba anions. Compounds (1) and (2) exhibit enhanced fluorescence emission. A study of the known s-block metal compounds containing 4-nba and coordinated water ligands reveals that the coordination number of the central metal varies from four in Li to nine in Ba.