Double mu(2)-(phenoxido)-bridged dinuclear and polynuclear nickel(II) complexes: magnetic properties and DNA/protein interaction

One dinuclear and one 1D polymeric nickel(II) complex, namely {[Ni2(HL)2(pa)2(H2O)2]·DMF} (1) and {[Ni2(HL)2(ppda)(H2O)2]·DMF·H2O}n (2) (H2L = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol, pa = 3-phenylacrylate, ppda = p-phenylenediacrylate) have been synthesized and characterized by X-ray single crystal structure determination. Complex 1 is double phenoxo-bridged dinuclear Ni(II) complex, whereas complex 2 is a 1D polynuclear chain where double phenoxo-bridged dinuclear units are connected through bridging ppda ligands. The variable temperature magnetic behavior of the complexes was studied using the Hamiltonian H = −JS1S2, S1 = S2 = SNi and confirms the presence of an overall antiferromagnetic interaction in both complexes. Good agreement between the experimental and simulated curves were found using the parameters: gNi = 2.15, DNi = 4.0 cm−1 and JNi-Ni = −0.60 cm−1 for 1, and gNi = 2.15, DNi = 4.8 cm−1 and JNi-Ni = −3 cm−1 for 2. The interactions of the complexes with CT-DNA were investigated using UV-Vis absorption and fluorescence spectroscopic methods and they show that both the complexes interact with CT-DNA. The intrinsic binding constants values for interaction with CT-DNA are 3.9(±0.10) × 105 and 3.43(±0.09) × 105 M−1 for 1 and 2, respectively. The interactions of the complexes with bovine serum albumins (BSA) and human serum albumins (HSA) were also studied using electronic absorption and fluorescence spectroscopic techniques and the results show that both complexes interact with the serum albumins via a ground state association process

DNA/protein binding and magnetic properties of a 1D Cu(II) complex containing fumarate and tridentate Schiff base ligands

ID copper(II) complex, [Cu2(L)2(fum)]∙H2O}n (1) has been synthesized using fumarate (fum2-) and a Schiff base (HL), derived from the condensation reaction of 2-amino-1-butanol and salicyldehyde. Complex 1 has been characterized by X-ray crystal structure, FT-IR, electronic absorption and fluorescence spectroscopic methods. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group P21/n and form 1D polymeric chain, built by bridging fum. Weak π¿π and C-H¿π interactions in 1, lead to a 3D supramolecular architecture. Complex 1 exhibits fluorescence at room temperature with a quantum yield (Φs) of 0.257. The interactions of complex 1 with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic techniques and the analysis shows that complex 1 interaction with BSA / HSA occurs mainly with ground state association process. Calculated values of apparent association constants are 1.34 × 104 M-1 and 1.81 × 104 M-1 for BSA and HAS, respectively, at 300 K. The number of binding sites and binding constants were calculated using double logarithm regression equation. The interaction of complex 1 with the calf thymus DNA (CT-DNA) was also investigated using electronic absorption and fluorescence spectroscopic methods. The results show that complex 1 has binding affinity to CT-DNA in the order of 2.96×105 M-1. Low temperature magnetic measurements reveal existence of antiferromagnetic interaction in complex 1. The magnetic data have been fitted considering complex 1 as a pseudo-dinuclear system, with the two copper(II) atoms bridged by two carboxylate oxygen atoms, since the coupling through long fum bridge is almost nil. The best-fit parameters obtained with this model are J = - 60 cm-1, gCu = 2.20

Structural and magnetic characterization of three tetranuclear Cu(II) complexes with face-sharing-dicubane/double-open-cubane like core framework

Three novel tetranuclear copper(II) complexes namely [Cu4(L1)4]∙(dmf) (1), [Cu4(L1)4] (2) and [Cu4(L2)2(HL2)2(H2O)2]∙2(ClO4)∙6(H2O) (3) (H2L1, (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H2L2, (E)-2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol)) were synthesised from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligands. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group C2/c, whereas both the complexes 2 and 3 crystallize in the triclinic system with space group P-1. Complexes 1 and 2 possess face-sharing dicubane core, on the other hand complex 3 has double open cubane core structure. The copper(II) ions in the cubane core are in distorted square planar geometries, and weak π¿π and C-H¿π interactions lead to formation of a 2D supramolecular architecture for complexes 1 and 2. At room temperature complexes 1, 2 and 3, exhibit fluorescence with a quantum yield (Φs) of 0.47, 0.49 and 0.38, respectively. Variable temperature magnetic susceptibility measurements in the range 2-300 K indicate an overall weak antiferromagnetic exchange coupling in all complexes. The PHI program was used to study their magnetic behaviour. In agreement with their face-sharing dicubane structure, a Hamiltonian of the type H = - J1(S1S2+S1S2'+S1'S2+S1'S2') - J2S1S1', where S1 = S1' = S2 = S2' = SCu = 1/2, was used for studying complexes 1 and 2. Simulations performed suggest magnetic exchange constants with values close to J1 = -20 cm-1 and J2 = 0 cm-1 for these complexes. On the other hand, the spin Hamiltonian H = - J1(S1S4+S2S3) - J2(S1S3+S2S4) - J3S1S2, where S1 = S2 = S3 = S4 = SCu = 1/2, was used to study the magnetic behaviour of the double open cubane core of complex 3 and a good agreement between the experimental and simulated results was found by using the parameters g1 = g2 = 2.20, g3 = g4 = 2.18, J1 = -36 cm-1, J2 = -44 cm-1 and J3 = 0 cm-1

Structural and magnetic characterization of two tetranuclear Cu(II) complexes with closed‐cubane‐like core framework

Two novel tetranuclear Cu(II) complexes [Cu4(L1)4]·3(H2O) (1) and [Cu4(H2L2)4(H2O)4] (2) ( H2L1 = (E)-2-((1-hydroxybutan-2-ylimino)methyl)phenol; H4L2 = 2-((2-hydroxy-3-methoxybenzylidene)amino)-2-hydroxymethylpropane-1,3-diol) were synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligands. Both complexes crystallize in the tetragonal system with space group I 41/a and form tetranuclear species with closed-cubane like core framework. Both the complexes possess a S4 axis but of different stereochemistry due to the different arrangement of the ligands about the copper ions. Variable temperature magnetic susceptibility measurements indicate an overall weak antiferromagnetic exchange coupling in 1, while ferromagnetic exchange coupling in 2. In agreement with their closed-cubane structure, the magnetic behavior of the two complexes have been studied by employing the isotropic spin Hamiltonian of type H = J1 (S1S3 + S1S4 + S2S3 + S2S4) - J2 (S1S2 + S3S4) (J1 describes the magnetic exchange coupling between the four Cu(II) pairs with short Cu···Cu distances, while J2 characterizes the magnetic exchange coupling between the remaining two intermetallic pairs with long distances). The PHI program was used to study their magnetic behavior. A good agreement between the experimental and fitted curves was found with the following parameters: g = 2.14, J1 = -20.3 cm-1 and J2 = 0 cm-1 for 1 and g = 2.10, J1 = 101.1 cm-1 and J2 = -51.5 cm-1 for 2

Synthesis, crystal structure and DNA/protein binding of tetranuclear Cu(II) complexes with a double-open-cubane like core framework

The copper(II) complexes [Cu4(L)2(HL)2(H2O)2]∙2(ClO4)∙2(H2O)∙DMF (1) and [Cu4(L)2(HL)2(H2O)2]∙(tp) (2) [H2L = 2-ethoxy-6-[(1-hydroxymethyl-propylimino)-methyl]-phenol; tp = terephthalate] have been synthesized and characterized by single crystal X-ray diffraction and spectroscopic studies. The structural determination reveals that both the complexes are tetranuclear with a double-open-cubane like core framework. The 2D supramolecular structure of 1 and 3D supramolecular structure of 2 are formed through C-H...π and hydrogen bonding interactions, respectively. At room temperature both the complexes exhibit fluorescence with quantum yields of 0.41 and 0.40. The interactions of the complexes with calf thymus DNA (CT-DNA) and serum albumins were investigated using electronic absorption and fluorescence spectroscopic techniques. The studies revels that the binding affinities of 1 and 2 with CT-DNA are of the order 8.86×105 M-1 and 7.14×105 M-1, respectively. Additionally, the interaction of the complexes with bovine serum albumin and human serum albumin were studied and the number of binding sites and binding constants were calculated using a double logarithm regression equation. The redox activities of the complexes were investigated in methanol solution by cyclic voltammetry

DNA/protein binding and magnetic properties of a 1D Cu(II) complex containing fumarate and tridentate Schiff base ligands

The 1D copper(II) complex [Cu2(L)2(fum)]·(H2O)·(MeOH)n(1) has been synthesized using fumarate (fum2−) and a Schiff base (HL), derived from the condensation reaction of 2-amino-1-butanol and salicylaldehyde. Complex 1 has been characterized by its X-ray crystal structure, together with FT-IR, electronic absorption and fluorescence spectroscopic methods. The structural determination reveals that complex 1 crystallizes in the monoclinic system with the space group P21/n and forms a 1D polymeric chain, built by bridging fum ligands. Weak π⋯π and C–H⋯π interactions lead to the formation of a 3D supramolecular architecture. Complex 1 exhibits fluorescence (λex, 366 nm; λem, 410, 433 and 462 nm) at room temperature, with a quantum yield (Φs) of 0.257. The interactions of complex 1 with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic techniques, and the results show that the interaction of complex 1 with BSA/HSA occurs mainly with a ground state association process. The calculated values of the apparent association constants (at 300 K) are 1.34 × 104and 1.81 × 104L mol−1for interactions with BSA and HSA, respectively. The number of binding sites and binding constants were calculated using a double logarithm regression equation. The interaction of complex 1 with calf thymus DNA (CT-DNA) was also investigated using electronic absorption and fluorescence spectroscopic methods. The results show that complex 1 has a binding affinity to CT-DNA of the order of 2.96 × 105L mol−1. Low temperature magnetic measurements reveal the existence of an antiferromagnetic interaction in complex 1. The magnetic data have been fitted considering complex 1 as a pseudo-dinuclear system, with the two copper(II) ions bridged by two carboxylate oxygen atoms, since the coupling through long fum bridge is almost nil. The best-fit parameters obtained with this model are J = −60 cm−1and gCu= 2.20

Structural and magnetic characterization of three tetranuclear Cu(II) complexes with face-sharing-dicubane/double-open-cubane like core framework

Three novel tetranuclear copper(II) complexes namely [Cu4(L1)4]â\u88\u992(dmf) (1), [Cu4(L1)4] (2) and [Cu4(L2)2(HL2)2(H2O)2]â\u88\u992(ClO4)·6(H2O) (3) (H2L1, (E)â\u88\u922-((1-hydroxybutan-2-ylimino)methyl)phenol; H2L2, (E)â\u88\u922-((1-hydroxybutan-2-ylimino)methyl)â\u88\u926-methoxyphenol)) were synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligands. The structural determination reveals that complex 1 crystallizes in the monoclinic system with space group C2/c, whereas both the complexes 2 and 3 crystallize in the triclinic system with space group P-1. Complexes 1 and 2 possess face-sharing dicubane core, on the other hand complex 3 has double open cubane core structure. The copper(II) ions in the cubane core are in distorted square planar geometries, and weak Ï\u80â\u80¦Ï\u80 and Câ\u80\u93Hâ\u80¦Ï\u80 interactions lead to formation of a 2D supramolecular architecture for complexes 1 and 2. At room temperature complexes 1, 2 and 3, exhibit fluorescence with a quantum yield (Φs) of 0.47, 0.49 and 0.38, respectively. Variable temperature magnetic susceptibility measurements in the range 2â\u80\u93300 K indicate an overall weak antiferromagnetic exchange coupling in all complexes. The PHI program was used to study their magnetic behaviour. In agreement with their face-sharing dicubane structure, a Hamiltonian of the type H =â\u80\u93 J1(S1S2+S1S2â\u80\u99+S1'S2+S1'S2â\u80\u99) â\u80\u93 J2S1S1â\u80\u99, where S1= S1â\u80\u99= S2= S2â\u80\u99= SCu=1/2, was used for studying complexes 1 and 2. Simulations performed suggest magnetic exchange constants with values close to J1=â\u88\u9220 cmâ\u88\u921and J2=0 cm-1for these complexes. On the other hand, the spin Hamiltonian H =â\u80\u93 J1(S1S4+S2S3) â\u80\u93 J2(S1S3+S2S4) â\u80\u93 J3S1S2, where S1= S2= S3= S4= SCu=1/2, was used to study the magnetic behaviour of the double open cubane core of complex 3 and a good agreement between the experimental and simulated results was found by using the parameters g1= g2=2.20, g3= g4=2.18, J1=â\u88\u9236 cm-1, J2=â\u88\u9244 cm-1and J3=0 cm-1

Manganese(IV) complex with a polydentate Schiff base ligand: synthesis, crystal structure, TDDFT calculation, electronic absorption and EPR spectral study

A six-coordinate Mn(IV) complex, [Mn(H2L)2] (1) [H4L = 2-methoxy-6-(tris(hydroxymethyl)methyliminomethyl)phenol], was synthesized and characterized by elemental analysis, single-crystal X-ray crystallography, FTIR, UV\u2013Vis electronic absorption, and EPR spectroscopy. The single-crystal structural determination reveals that the complex crystallizes in tetragonal space group P41212 and the tridentate Schiff base ligands are arranged in mer configuration chelating manganese, which exhibits as slightly distorted octahedral coordination sphere with a N2O4 chromophore. Weak hydrogen bonding interactions of uncoordinated hydroxyl groups result in a 2-D supramolecular structure. The UV\u2013Vis electronic absorption and IR spectral data of 1 have been compared with the results obtained by employing DFT and time-dependent density functional theory calculation using B3LYP, B3PW91, and MPW1PW91 functionals, with 6-31G (d-p) and LanL2MB basis sets. The results of these calculations are functional-dependent and, among those used, B3PW91 proved to better reproduce the experimental results