Late metal salicylaldimine complexes derived from 5-aminosalicylic acid — Molecular structure of a zwitterionic mono Schiff base zinc complex

Condensation of salicylaldehyde (2-HOC 6 H 4 C(O)H) with 5-aminosalicylic acid (5-H 2 NC 6 H 3 -2-(OH)-CO 2 H) afforded the Schiff base 2-HOC 6 H 4 C(H)=NC 6 H 3 -2-(OH)-5-CO 2 H ( a ). Similar reactivity with 5-bromosalicylaldehyde was also observed to give 5-Br-2-HOC 6 H 3 C(H)=NC 6 H 3 -2-(OH)-5-CO 2 H ( b ). Reaction of these salicylaldehydes with Pd(II), Cu(II), and Zn(II) salts gave the corresponding bis(N-arylsalicylaldiminato)metal complexes (M = Pd ( 1 ), Cu ( 2 ), Zn ( 3 )). The molecular structure of the Schiff base compound a has been confirmed by an X-ray diffraction study. Crystals of a were monoclinic, space group P2(1)/c, a = 7.0164(7) Å, b = 11.0088(11) Å, c = 14.8980(15) Å, β = 102.917(2)°, Z = 4. The molecular structure of a novel zwitterionic conformer of 3a was also characterized by an X-ray diffraction study. Crystals of 4 were monoclinic, space group P2(1)/c, a = 9.5284(5) Å, b = 19.5335(11) Å, c = 8.6508(5) Å, β = 90.596(1)°, Z = 4. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus. Key words: 5-aminosalicylic acid (5-ASA), antifungal, copper, palladium, salicylaldimines, Schiff base, zinc.