Mapping of Solvent-Mediated Molecular Self-Assembly of Iron(III) Discrete Compounds: Exploring Their Magnetic Behavior and Phosphatase-Like Activity

Abstract

Two newly synthesized Fe(III) based complexes, [Fe 4 L 2 (μ 3 -O) 2 (Cl) 2 (MeOH) 4 (H 2 O) 4 ](ClO 4 ) 2 •4H 2 O•MeOH (1) and [Fe 2 L 3 ]•4DMF (2) were isolated in solid crystalline form using the reaction of iron(III) perchlorate with the ligand H 2 L (H 2 L = 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(2-methoxyphenol). (DMF= N,N-dimethylformamide, MeOH = methanol). Compound 1 was self-assembled in MeOH, but when the solvent was changed to DMF, compound 2 was harvested. Furthermore, compound 1 was converted to compound 2 just by dissolving compound 1 in DMF. Sequential self-assembly and conversion of compound 1 to 2 were monitored by UV−vis spectroscopy and ESI-Mass spectroscopy in solution phase. Single crystal X-ray analysis showed that compound 1 has μ 3 -oxo bridged tetranuclear structure whereas compound 2 has puckered dinuclear structure. Magnetic studies indeed revealed frustrated magnetic spin for compound 1 whereas antiferromagnetic interaction was observed for compound 2. The spectrophotometrical investigation on their phosphatase like activity revealed remarkable hydrolytic efficiency for both the complexes. Michaelis−Menten-derived kinetic parameters suggest the competitiveness of the rate of P−O bond fission employing the phosphomonoester (4-nitrophenyl)phosphate (PNPP) in 97.5% DMF is 1 > 2, and the k cat value lies in the range 28.95−38.43 s −1 at 298 K. Computational calculations have verified the higher catalytic activity of compounds 1 over 2 attributed to the large number of labile groups attached to the metal centers.

Executing a Series of Zinc(II) Complexes of Homologous Schiff Base Ligands for a Comparative Analysis on Hydrolytic, Antioxidant, and Antibacterial Activities

“…Phosphatase is an assemblage of hydrolytic enzymes that catalyze the dephosphorylation reaction, that is, hydrolysis of phosphate monoesteric, diesteric, and triesteric P–O bonds − This is one of the essential biological reactions, as this is involved in cellular signaling, synthesis of proteins, replication of genetic material to energy, and so forth. , The uncatalyzed hydrolysis is extremely slow and the cleavage of P–O bonds is accelerated in the presence of bivalent metal ions. − Over the last few decades, many groups including our group have been involved in designing the bio-mimicking models to establish plausible mechanistic pathways of phosphatase activity. − Generally, dinuclear complexes are more efficient than their mononuclear counterparts because two metal centers may act mutually in substrate binding to catalyst, activation of the nucleophile, and cleavage of the bond. − The availability of a nucleophile (water or hydroxo) in the close vicinity of the metal center(s) is the predominant factor of phosphatase activity and attack of nucleophile on the phosphorus center is the rate-determining step of hydrolysis . The other factors that dictate the rate of hydrolysis are reaction conditions, Lewis acidity of metal centers, stereochemistry, presence of oxo-anions, the coordination domain of metal ions, and the presence of electronegative atoms in the ligand backbone. − In recent times, designing of bio-mimicking models with additional biological applications always draws special attention of the bio-inorganic chemists . The incorporation of metals to the ligand system enhanced the biological activity of the overall entity.…”

Ni(II)-Complex Anchored onto Magnetically Separable Oxidized Single-Walled Carbon Nanohorn: A DFT-Supported Mechanistic Approach for Hydrogen-Borrowing Quinoxaline Synthesis

“…The successful incorporation of the −COOH functional group was also confirmed by the presence of a broad band at 3408 cm –1 for the O–H stretching mode, with the disappearance of the absorption band centered at 2800–3000 cm –1 revealing the fact that sp 2 –C is the main reaction center where oxidation usually takes place . Amalgamation of spinel NiFe 2 O 4 and l -dopa onto the surface of functionalized SWCNHs was further proved by the newly generated absorption peaks located at 466 and 590 cm –1 for T d Ni II –O and O h Fe III –O stretching, 590 cm –1 for O h, 3372 cm –1 for the overlapping of N–H and O–H stretching modes assuring the binding of l -dopa, and most importantly 1743 cm –1 which confirms the anchoring of NiFe 2 O 4 with COO – of SWCNHs. , In the IR spectrum of the catalyst FNHDNi , two new bands are observed at 3024 and 1629 cm –1 due to sp 2 –C–H in the benzene ring of complex 1 , overlapping of –CO of amide and –CN of imine stretching – of the azomethyne group in the Schiff base complex, respectively, along with presence of metal-coordinated H 2 O molecule in complex 1, supported from the absorption band ∼3400 cm –1 , thereby firmly indicating the amidation reaction between l -dopa and the piperazine N atom of NiL 1 . Furthermore, the bands near 1370 and 1550 cm –1 for the presence of nitrate and nitro groups, respectively, strongly support the fruitful construction of the heterogeneous magnetic catalyst FNHDNi .…”

Iron Complexes Anchored onto Magnetically Separable Graphene Oxide Sheets: An Excellent Catalyst for the Synthesis of Dihydroquinazoline-Based Compounds

“…Immediate precipitation of H 2 L 2 occured. To this precipitate was added 10 mL of methanolic solution of iron chloride hexahydrate (0.135 g, 0.5 mmol) . A yellow precipitate of H 2 L 2 disappeared immediately to generate a wine red solution.…”