Structural diversity in Ni^II cluster chemistry: Ni₅, Ni₆, and {NiNa₂}_n complexes bearing the Schiff-base ligand N-naphthalidene-2-amino-5-chlorobenzoic acid

Abstract

The employment of the fluorescent bridging and chelating ligand N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2) in Ni(II) cluster chemistry has led to a series of pentanuclear and hexanuclear compounds with different structural motifs, magnetic and optical properties, as well as an interesting 1-D coordination polymer. Synthetic parameters such as the inorganic anion present in the NiX2 starting materials (X = ClO4(-) or Cl(-)), the reaction solvent and the nature of the organic base employed for the deprotonation of nacbH2 were proved to be structure-directing components. Undoubtedly, the reported results demonstrate the rich coordination chemistry of nacbH2 in the presence of Ni(II) metal ions and the ability of this chelate to adopt a variety of different modes, thus fostering the formation of high-nuclearity molecules with many physical properties.

Rare Nuclearities in Ni(II) Cluster Chemistry: An Unprecedented {Ni12} Nanosized Cage from the Use of N-Naphthalidene-2-Amino-5-Chlorobenzoic Acid

“…Both features presage the synthesis of new cluster compounds with potentially interesting magnetic and emission properties. Indeed, the initial employment of nacbH2 in Ni II chemistry has afforded a series of {Ni5} and {Ni6} clusters with diverse magnetic and optical properties, but with limited bridging affinity for nacb 2− [14]. In this work, we have unveiled the bridging capacity of nacb 2− in conjunction with ancillary bridging benzoate groups.…”

“…The dodecanuclear compound 1 exhibits a cyan-to-green centered emission at 520 nm, upon maximum excitation at 380 nm ( Figure 7). The red-shifted emission of 1 with respect to the free nacbH 2 can be tentatively assigned to the coordination of the deprotonated nacb 2− ligands with the metal ions and/or the presence of additional binding groups with emission efficiency, such as benzoates, which could affect the charge transfer process and resulting emission [14,15].…”

“…All manipulations were performed under aerobic conditions using materials (reagent grade) and solvents as received unless otherwise noted. The Schiff base ligand nacbH 2 was prepared, purified, and characterized as described elsewhere [14,15]. Elemental analyses (C, H, and N) were performed on a Perkin-Elmer 2400 Series II Analyzer (Foster City, CA, USA).…”

4f-Metal Clusters Exhibiting Slow Relaxation of Magnetization: A {Dy7} Complex with An Hourglass-like Metal Topology

“…Based on these findings, we have decided to turn our attention to the chemically and electronically similar ligand N-naphthalidene-2-amino-5-chlorobenzoic acid (nacbH2, Scheme 1), which is sterically though more rigid, and its solubility in organic solvents differs significantly from that of sacbH2. These combined factors were the main reasons for the isolation and structural characterization of a series of totally different 3d-metal/nacb 2− clusters [21,22] when compared to the obtained results from similar systems with sacbH2 chelate.…”

“…All manipulations were performed under aerobic conditions using materials (reagent grade) and solvents as received unless otherwise noted. The Schiff base ligand nacbH 2 was prepared, purified and characterized as described elsewhere [21,22]. Infrared spectra were recorded in the solid state on a Bruker's FT-IR spectrometer (ALPHA's Platinum ATR single reflection, in the 4000-400 cm −1 range.…”