4,4′‐bipyridine bridged two Cu (II) complexes, [Cu2L12(4,4′‐bipy)(H2O)2](ClO4)2 (1) and [Cu2L22(4,4′‐bipy)]n·(2H2O)n (2) (where, HL1 = 2‐[(3‐methylamino‐propylimino)‐methyl]‐phenol, H2L2 = 3‐[(2‐hydroxy‐3‐methoxy‐benzylidene)‐amino]‐propionic acid, and 4,4′‐bipy = 4,4′‐bipyridine) have been synthesized and characterized by single crystal structure determination, mass spectrometry, FT‐IR, electronic absorption, and emission spectroscopy. Complex 1 is dinuclear cationic compound and counter balanced by perchlorate anion, whereas complex 2 possesses 1D poly‐nuclear structure. Both the complexes crystallize in monoclinic system with P21/c space group and the copper centers possess square pyramidal geometry. H‐bonding, C‐H···π, π···π interactions results the formation of two dimentional supramolecular structure for both the complexes. Interactions of complexes with bovine serum albumins (BSA) and human serum albumins (HSA) have been studied by using electronic absorption and emission spectroscopic technique. The calculated values of binding constants (Kb) are (9.22 ± 0.26) × 105 L mol−1 (1‐BSA), (7.19 ± 0.16) × 105 L mol−1 (1‐HSA), (5.05 ± 0.20) × 105 L mol−1 (2‐BSA) and (3.56 ± 0.25) × 105 L mol−1 (2‐HSA). The mechanism of serum albumins‐complex interactions have been investigated by fluorescence lifetime measurement. Fluorescence spectroscopic studies indicate that both the complexes interact with calf thymas‐DNA. Catecholase activity of the complexes has been studied in methanol using 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) as substrate and the result show that both the complexes are active for catalytic oxidation of 3,5‐DTBC to 3,5‐di‐tert‐butylquinone (3,5‐DTBQ) in presence of molecular oxygen. Calculated values of turnover numbers are 71.81 ± 1.04 h−1 and 69.45 ± 0.74 h−1 for 1 and 2, respectively.
Two CoII–CoIII mixed‐valance complexes of molecular formulas [Co2(H2L)2(H2O)2][Co2(H2L)2(H2O)(m‐phth)]·8(H2O) {1; H2L2– = 2‐[(2‐hydroxy‐3‐methoxybenzylidene)amino]‐2‐(hydroxymethyl)propane‐1,3‐diolato, m‐phth = 1,3‐benzenedicarboxylate} and [Co4(H2L)4(H2O)2(ppda)]·2(dmf)·3.2(H2O) {2; ppda = 1,4‐phenylenediacrylate; dmf = N,N‐dimethylformamide} were synthesized and characterized by single‐crystal X‐ray diffraction and magnetic studies at low temperature. The structural determination reveals that 1 is composed of dinuclear ion pairs, namely, a cationic [Co2(H2L)2(H2O)2]+ (1+) and an anionic [Co2(H2L)2(H2O)(m‐phth)]– (1–) unit. In each of these ions, the CoII and CoIII centers present distorted octahedral geometries. Compound 2 is a centrosymmetric tetranuclear complex comprising two symmetry‐related dinuclear CoII–CoIII units bridged by ppda anions. Alternating current/direct current (ac/dc) magnetic studies revealed that the individual CoII–CoIII unit exhibits field‐induced slow magnetic relaxation consistent with single‐ion magnet (SIM) behavior. Ab initio NEVPT2 calculations confirm large zero‐field splitting (zfs) from a first‐order spin–orbit coupling (SOC) in both complexes (D = –62.4, –95.8, and –101.9 cm–1 and E/D = 0.219, 0.216, and 0.234 for 1+, 1–, and 2, respectively).
Distorted square pyramidal complexes [Cu(L1)(H2O)]·ClO4 (1), [Cu(L2)(H2O)]·ClO4 (2) and [Cu(L3)(H2O)]·ClO4 (3) (HL1 = o-{[2-(2-aminoethylamino)ethylimino]methyl}phenol; HL2 = 2-{[2-(2-aminoethylamino)ethylimino]methyl}-6-methoxyphenol; HL3 = o-{1-[2-(2-aminoethylamino)ethylimino]ethyl}phenol) have been synthesized, and characterized by X-ray crystallography and spectroscopic analysis. All the complexes exhibit fluorescence at room temperature [λex = 267 nm, λem = 312, 329 and 357 nm, φ = 0.52 for 1; λex = 272 nm, λem = 312, 329 and 355 nm, φ = 0.46 for 2; λex = 265 nm, λem = 312, 356 and 377 nm, φ = 0.33 for 3]. The electronic structure and photophysical properties of the ligands and complexes were calculated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods using the B3LYP, B3PW91 and MPW1PW91 functionals, with 6-31G (d-p) and LanL2DZ basis sets. The results of TD-DFT calculations are functional-dependent and among the functionals, B3LYP was able to best reproduce the experimental results. Catecholase activity of 1-3 has been investigated using 3,5-di-tert butyl catechol (3,5-DTBC) as the model substrate and found that complexes are active for catalyzing the aerobic oxidation of 3,5-DTBC to 3,5-di-tert butyl benzoquinone (3,5-DTBQ). The compound with more distorted square pyramidal geometry shows a higher rate of catalytic activity. All the complexes have been tested for their anticancer activities in human breast (MCF7) cancer cell lines. Complexes show dose dependent suppression of cell viability with IC50 values 30, 68 and >100 μM for 1, 2 and 3, respectively. Anticancer activities of 1-3 and cisplatin were compared, and found that 1-3 were relatively less active than cisplatin
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