Two new complexes of nickel (II) with 4-amino-3, 5-bis(pyridyl)-1, 2, 4-triazole (abpt) and iron (II) with 2-(3-phenyl-1H-pyrazole-5-yl) pyridine (phpzpy) have been synthesized and characterized by elemental analysis and IR spectroscopy. The crystal structures of the complexes have been determined by single crystal X-ray diffraction techniques. In the nickel and iron complexes, the ligands are coordinated through nitrogen atoms in bidentate manner. The ligands and their respective complexes have been tested for their antifungal activity against Aspergillus niger, Aspergillus flavus, and Candida albicans. From the study, the complexes showed enhanced activities against the tested organisms compared to the ligands. 1. Introduction Aromatic nitrogen heterocycles represent an important class of compounds which can act as ligands towards metal ions [1]. Azoles belong to this class and are five-membered heterocyclic ligands containing two or more heteroatoms, one of which must be nitrogen. These compounds have been paid considerable attention due to their wide applicability in medicine [2–4]. Pyrazole and triazole derivatives are subject of many research studies due to their widespread potential biological activities such as antitumour [5, 6], anti-inflammatory [7], antipyretic [8], antivirial [9], antimicrobial [10, 11], anticonvulsant [12], antihistaminic [13], antidepressant [14, 15], insecticides, and fungicides. In coordination chemistry pyrazole-and triazole-derived ligands exhibit various coordination modes and have received considerable attention for the synthesis of transition metal complexes with various nuclearities [16]. Herein we report on the synthesis, structural determination, and antifungal activities of Ni(II) and Fe(II) complexes of abpt and phpzpy, respectively. The crystal structures of the complexes are described and compared with those of closely related structures. 2. Experimental 2.1. Materials and Physical Measurements Elemental analysis for carbon, hydrogen, and nitrogen was performed on a Thermo Flash EA-1112 Series CHNS-O Elemental Analyzer. The IR spectra were obtained from KBr pellets in the range 4000–400？cm？1 using a Perkin-Elmer Spectrum 100？FT-IR spectrometer. 2.2. Single Crystal X-Ray Diffraction Analysis and Structure Determination Suitable-single crystals of 1 and 2 were selected and mounted in air onto a loop. The data collection for 1 and 2 was carried out with a Bruker DUO APEX II CCD diffractometer at 173 ？K using an Oxford cryostream 700. Data reduction and cell refinement were performed using SAINT-Plus, [17–21] and
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