Rare Nuclearities In Ni(Ii) Cluster Chemistry: An Unprecedented {Ni-12} Nanosized Cage From The Use Of N-Naphthalidene-2-Amino-5-Chlorobenzoic Acid

The self-assembly reaction between NiI2, benzoic acid (PhCO2H) and the Schiff base chelate, N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH(2)), 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 similar to 30% yield. Complex 1 has a cage-like conformation, comprising twelve distorted, octahedral Ni-II ions that are bridged by five mu(3)-OH-, one mu-OH-, an I- in 55% occupancy, five PhCO2- groups (under the eta(1):eta(1):mu, eta(1):eta(2):mu(3) and eta(2):eta(2):mu(4) modes), and the naphthoxido and carboxylato O-atoms of five doubly deprotonated nacb(2-) groups. The overall {Ni-12} cluster exhibits a nanosized structure with a diameter of similar to 2.5 nm and its metallic core can be conveniently described as a series of nine edge- or vertex-sharing {Ni-3} triangular subunits. Complex 1 is the highest nuclearity coordination compound bearing the nacbH(2) chelate, and a rare example of polynuclear Ni-II complex containing coordinating I- ions. Direct current (DC) magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Ni-II 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 nacb(2-) chelate in the presence of Ni-II metal ions, and the ability of this ligand to adopt a variety of different bridging modes, thus fostering the formation of high-nuclearity molecules with rare, nanosized dimensions and interesting physical (i.e., magnetic and optical) properties.