Rare nuclearities in Ni(II) cluster chemistry: an unprecedented {Ni12} nanosized cage from the use of N-naphthalidene-2-amino-5-chlorobenzoic acid.

Abstract

The self-assembly reaction between NiI2, benzoic acid (PhCO2H) and the Schiff base chelate, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2), in the presence of the organic base triethylamine (NEt3), has resulted in the isolation and the structural, spectroscopic, and physicochemical characterization of the dodecanuclear [Ni12I2(OH)6(O2CPh)5(nacb)5(H2O)4(MeCN)4]I (1) cluster compound in ~30%yield. Complex 1 has a cage-like conformation, comprising twelvedistorted, octahedral NiII ions that are bridged by five 3-OH􀀀, one -OH􀀀, an I􀀀 in 55% occupancy, five PhCO2􀀀 groups (under the 1: 1: , 1: 2: 3 and 2: 2: 4 modes), and the naphthoxido and carboxylato O-atoms of five doubly deprotonated nacb2􀀀 groups. The overall {Ni12} cluster exhibits a nanosized structure with a diameter of ~2.5 nm and its metallic core can be conveniently described as a series of nine edge- or vertex-sharing {Ni3} triangular subunits. Complex 1 is the highest nuclearity coordination compound bearing the nacbH2 chelate, and a rare example of polynuclear NiII complex containing coordinating I􀀀 ions. Direct current (DC) magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the NiII ions, while photophysical studies of 1 in the solid-state showed a cyan-to-green centered emission at 520 nm, upon maximum excitation at 380 nm. The reported results demonstrate the rich coordination chemistry of the deprotonated nacb2􀀀 chelate in the presence of NiII metal ions, and the ability of this ligand to adopt a variety of di erent bridging modes, thus fostering the formation of high-nuclearity molecules with rare, nanosized dimensions and interesting physical (i.e., magnetic and optical) properties.