SCHIFF BASES ARE CONSIDERED AS AN IMPORTANT CLASS OF LIGANDS IN COORDINATION CHEMISTRY AND HAVE EXTENSIVE APPLICATIONS IN DIFFERENT FIELDS. THEY READILY COORDINATE WITH A WIDE RANGE OF TRANSITION METAL IONS, YIELDING STABLE AND INTENSELY COLORED METAL COMPLEXES, WHICH EXHIBIT INTERESTING PHYSICAL, CHEMICAL, BIOLOGICAL AND CATALYTIC PROPERTIES [1, 2]...

IRON AND ZINC MODEL COMPLEXES ARE IMPLICATED AS KEY INTERMEDIATES IN SEVERAL SYNTHETIC AND BIOCHEMICAL CATALYTIC CYCLES OF SOME METALLOENZYMES [1-2]. IN THIS WORK, SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF SUCH THESE COMPLEXES ARE REPORTED. TREATMENT OF THE REDOX-ACTIVE IMINOPHENOL-IMINOPYRIDINE HYBRID LIGAND, HLIPIP WITH IRON CHLORIDE AND ZINC ACETATE AFFORDED NEW IRON AND ZINC COMPLEXES, RESPECTIVELY. THE STRUCTURE AND PHYSICAL PROPERTIES OF THE SYNTHESIZED COMPLEXES HAVE BEEN EXAMINED IN DETAIL BY X-RAY, FT-IR, UV-VIS AND CYCLIC VOLTAMMETRY. THE CRYSTAL STRUCTURE OF LIPIPFEO EXHIBITS A SQUARE-PYRAMIDAL GEOMETRY WITH THE FE CENTER COORDINATED BY THREE NITROGEN ATOMS, ONE PHENOLATE OXYGEN ATOM WITH A TERMINAL OXO LIGAND. IT IS EVIDENT FROM X-RAY CRYSTALLOGRAPHY ANALYSIS THAT LIPIPZNOAC EXISTS AS A DISTORTED SQUARE-PYRAMIDAL IN WHICH ZNII COORDINATED BY PYRIDINE, IMINE AS WELL AS ONE PHENOLATE. THE ACETATE GROUP OCCUPIES THE FIFTH POSITIONS IN LIPIPZNOAC (FIGURE 1). ELECTROCHEMICAL STUDIES CONDUCTED TO EVALUATE THE REDOX-ACTIVE BEHAVIOR OF THE COMPLEXES, SHOW A LIGAND-BASED OXIDATION PROCESS.

BACKGROUND: SCHIFF BASE LIGANDS HAVE BEEN EXTENSIVELY STUDIED IN COORDINATION CHEMISTRY MAINLY DUE TO THEIR FACILE SYNTHESES, EASILY TUNABLE STERIC, ELECTRONIC PROPERTIES, GOOD SOLUBILITY IN COMMON SOLVENTS AND FORMING STABLE COMPLEXES WITH MOST OF THE TRANSITION METALS [1]...

NOWADAYS NANOSTRUCTURE COMPOUNDS ARE OF INTEREST BECAUSE OF NOTABLE PROPERTIES WITH RESPECT TO BULK ONES. NANOMETER-SIZE PARTICLES OF METAL COORDINATION COMPLEXES ENHANCE THEIR PHYSICAL AND CHEMICAL PROPERTIES THAT MAY BE DUE TO THE LARGE NUMBER OF SURFACE MOLECULES WHEN ARE COMPARED WITH NON-NANOSTRUCTURE COMPOUNDS [1]..

THIOSEMICARBAZONE LIGANDS CAN COORDINATE IN A NUMBER OF DIFFERENT MANNERS. IN GENERAL, THEY ARE IN TWO TAUTOMERIC FORMS; A NEUTRAL THIONE FORM AND THIOLATE FORM.1, 2 METAL COMPLEXES WITH AN ONS DONOR SET ARE OF MUCH INTEREST BECAUSE OF THEIR POTENTIAL APPLICATIONS IN FUNDAMENTAL AND APPLIED SCIENCES.

THE COORDINATION CHEMISTRY OF PYRIDYL COMPLEXES OF TRANSITION METALS HAS BEEN EXTENSIVELY STUDIED DUE TO THEIR APPLICATIONS IN BIOCHEMICAL RESEARCH, SUPRAMOLECULAR CHEMISTRY AND PHOTOLUMINESCENCE STUDIES [1]. IN PARTICULAR, THE COORDINATION CHEMISTRY OF 2,2':6',2”-TERPYRIDINE (TPY) AND ITS DERIVATIVES HAS RECEIVED A GREAT DEAL OF ATTENTION OVER MANY DECADES. AS A TRIDENATE LIGAND, TPY FORMS MANY STABLE COMPLEXES BY A VARIETY OF TRANSITION METAL IONS [1-2]. IN THE PRESENT WORK, WE HAVE INVESTIGATED THE REACTION OF A SERIES OF 4'-SUBSTITUTED TERPYRIDYL LIGANDS (4'-X-TPY) TOWARD COPPER (II) AND ZINC (II) COMPOUNDS IN WHICH X CAN BRIDGE BETWEEN TWO METAL CENTERS, RESULTING IN THE FORMATION OF COORDINATION POLYMERS. THE PRODUCTS HAVE BEEN FULLY CHARACTERIZED BY ELEMENTAL ANALYSIS, IR, THERMOGRAVIMETRIC ANALYSIS (TGA) AND MASS SPECTROSCOPY. NOTABLY, WE HAVE FOUND THAT THE REACTION OF CUI WITH 4'-SUBSTITUTED TERPYRIDYL LIGANDS RESULTED IN THE FORMATION OF COPPER (II) COMPLEXES OF TERPYRIDINES. THE SOLID STATE X-RAY STRUCTURE DETERMINATION OF A SERIES OF ZN (II) AND CU (II) COMPLEXES WILL BE PRESENTED.

SCHIFF BASE LIGANDS HAVE ATTRACTED MUCH ATTENTION IN MEDICINAL INORGANIC CHEMISTRY IN VIEW OF THEIR DIVERSE BIOLOGICAL, PHARMACOLOGICAL, ANTITUMOR PROPERTIES AND THEIR EXCEPTIONAL CHELATING ABILITY [1, 2]. ZINC COMPLEXES OF THESE LIGANDS HAVE BEEN WIDELY STUDIED IN VARIOUS AREAS OF BIOINORGANIC CHEMISTRY SUCH AS ANTICANCER [3], UREASE INHIBITORY [4], AND ANTIOXIDANT [5] ACTIVITIES. MOREOVER, ZINC SCHIFF BASE COMPLEXES HAVE BEEN SUBJECT OF DEEP INVESTIGATION FOR DNA BINDING AND CLEAVAGE STUDIES [6]. THE RESULTS OF THESE STUDIES ARE PROMISING IN MOST CASES AND ALSO PRESENT THE BINDING OF METAL TO LIGAND REINFORCE ACTIVITY. IN CONTINUATION OF OUR PROGRAM [7] ON SYNTHESIS AND BIOLOGICAL ACTIVITY OF ZINC COMPLEXES WITH BIDENTATE SCHIFF BASE LIGANDS, IN THIS WORK WE WISH TO REPORT SYNTHESIS, SPECTRAL IDENTIFICATION, THERMAL BEHAVIORS AND ANTIMICROBIAL INVESTIGATION OF SOME NEW FOUR COORDINATED ZINC HALIDE AND PSEUDO-HALIDE COMPLEXES INCLUDING BIS((E)-3-(4- (DIMETHYLAMINO)PHENYL)ALLYLIDENE)BUTANE-1,4-DIAMINE AS A N2-DONOR SCHIFF BASE. THE NEWLY SYNTHESIZED LIGAND AND ITS COMPLEXES HAVE BEEN CHARACTERIZED ON THE BASIS OF ANALYTICAL AND SPECTROSCOPIC STUDIES SUCH AS FT-IR, 1H AND 13C NMR AND UV–VISIBLE. AFTER CHARACTERIZATION, THERMAL BEHAVIORS OF ALL COMPLEXES WERE INVESTIGATED AND THEN SOME THERMAL ACTIVATION PARAMETERS OF DECOMPOSITION PROCESSES WERE CALCULATED BY COATS–REDFERN EQUATION BASED ON TG/DTG/DTA DIAGRAMS. FURTHERMORE, THE BIOLOGICAL ACTIVITIES OF THE LIGAND AND ITS ZINC COMPLEXES AGAINST THE ESCHERICHIA COLI AND PSEUDOMONAS AERUGINOSA AS GRAM-NEGATIVE BACTERIA AND STAPHYLOCOCCUS AUREUS AND BACILLUS SUBTILIS AS GRAM-POSITIVE BACTERIA, AND THE TWO FUNGUSES ASPERGILLUSNIGER AND CANDIDA ALBICANS WERE SCREENED. ULTIMATELY, THE DNA CLEAVAGE STUDIES BY ELECTROPHORESIS METHOD WERE INVESTIGATED FOR ALL THE COMPOUNDS.

A NEW TRI-LINKED AZACROWN MACROCYCLE L2 WAS SYNTHESIZED FROM MONO MACROCYCLE ANALOGUE L1 [1] BY WILLIAMSON ETHERIFICATION AND CHARACTERIZED. THE REACTION ZINC (II) SALTS YIELDED CORRESPONDING COMPLEXES THAT FORMULATED AS ZNL1(OAC)2 (1) AND ZN3L2(OAC)6.3H2O (2) MONO AND TRINUCLEAR ZINC (II) COMPLEXES 1 AND 2, RESPECTIVELY, HAVE BEEN TESTED AS CATALYSTS FOR HYDROLYSIS OF 2-HYDROXYLPROPYL-4-NITROPHENYL PHOSPHATE (HNPP) [2]. THE EFFICIENCY OF TRINUCLEAR ZINC (II) COMPLEX 2 WAS STUDIED AT DIFFERENT PH VALUES (5, 7, AND 8.5) WITH RESPECT TO HNPP HYDROLYSIS AND COMPARED TO THE ACTIVITY OF MONONUCLEAR COMPLEX 1. WHILE AN IMPORTANT EFFECT OF PH ON THE HNPP HYDROLYSIS WAS OBSERVED FOR 2, THE MONONUCLEAR COMPLEX 1 EXHIBITED NO ACTIVITY AT THE CHOSEN THREE PH VALUES. FOR 2, ACTIVITY WAS OBSERVED ONLY AT PH 8.5. THEREFORE, THE HYDROLYSIS OF HNPP BY 2 WAS FOLLOWED BY THE VISIBLE ABSORBANCE CHANGE. INITIAL VELOCITIES (VI) WERE MEASURED BY FOLLOWING THE ABSORBANCE AT 400 NM DUE TO THE RELEASE OF 4-NITROPHENOLATE ANION [3]. AT PH 8.5 THE MONONUCLEAR COMPLEX 1 WAS FOUND TO BE INACTIVE. IN CONTRAST, KINETIC DIAGRAMS INDICATED THAT TRINUCLEAR COMPLEX 2 WAS HYDROLYZING PHOSPHODIESTER AND THE REACTION WAS UP TO 35–FOLD FASTER THAN THE UNPROMOTED REACTION.