ClO4 Complexes Research Articles

Synthesis and characterization of Cu(II)‑meso-HMPAO complex as a model for the development of potential 64Cu radiopharmaceutical

In this work, Cu(II) complexes with meso‑HMPAO and d,l-HMPAO were synthesized. The structural characterisation of the isolated compounds has been done by single-crystal X-ray diffraction analysis, FTIR, and mass spectroscopy. Redox properties of complexes and binding to deoxyribonucleic acid (DNA) molecule have been analysed in detail by cyclic voltammetry and DFT calculations. The results of cyclic voltammetry fully agree with the data obtained by DFT calculations and indicate that the first electron removal takes place from the metal, while the second electron is removed from the ligand. The formation of the complex leads to the shift in oxidation peaks of the ligand from ‒0.29 V to 0,47 V and from 1.18 V to 1,24 V, indicating that ligand in the complex is much more difficult to oxidize. Electrochemical data confirmed the binding between the complex and DNA molecules through guanine. DFT calculations show that the complex is suitable not only for binding purine and pyrimidine bases through a coordination bond but also for additional hydrogen and CH-π interactions of the bases with the ligand. The fluorescence titration experiments revealed a moderate binding affinity of the [Cu-HMPAO]ClO4 complex to human serum albumin (HSA). Molecular docking revealed that this ligand preferentially binds to drug binding site 3 of HSA. Therefore, the novel compounds could be of great interest for further investigation, considering the potential anticancer activity, and as a model for the development of radiopharmaceutical with 64Cu.

Oral administration of a new copper (I) complex with coumarin as ligand: modulation of the immune response and the composition of the intestinal microbiota in Onchorhynchus mykiss.

[Cu(NN1)2]ClO4 is a copper (I) complex, where NN1 is an imine ligand 6-((quinolin-2-ylmethylene) amino)-2H-chromen-2-one obtained by derivatization of natural compound coumarin, developed for the treatment of infectious diseases that affect salmonids. In previous research, we showed that the Cu(I) coordination complex possesses antibacterial activity against Flavobacterium psychrophilum, providing protection against this pathogen in rainbow trout during challenge assays (with an RPS of 50%). In the present study, the effects of administering [Cu(NN1)2]ClO4 to Oncorhynchus mykiss over a 60-days period were evaluated with regard to systemic immune response and its potential to alter intestinal microbiota composition. In O. mykiss, an immunostimulatory effect was evident at days 30 and 45 after administration, resulting in an increment of transcript levels of IFN-γ, IL-12, TNF-α, lysozyme and perforin. To determine whether these immunomodulatory effects correlated with changes in the intestinal microbiota, we analyzed the metagenome diversity by V4 16S rRNA sequencing. In O. mykiss, both [Cu(NN1)2]ClO4 and commercial antibiotic florfenicol had comparable effects at the phylum level, resulting in a predominance of proteobacteria and firmicutes. Nonetheless, at the genus level, florfenicol and [Cu(NN1)2]ClO4 complex exhibited distinct effects on the intestinal microbiota of O. mykiss. In conclusion, our findings demonstrate that [Cu(NN1)2]ClO4 is capable of stimulating the immune system at a systemic level, while inducing alterations in the composition of the intestinal microbiota in O. mykiss.

Copper(I) complexes of 1,2-bis(diphenylphosphino)benzene as efficient catalysts for alkyne hydroamination and azide-alkyne cycloaddition

This paper reports the synthesis of a small group of three copper(I) complexes using 1,2-bis(diphenylphosphino)benzene, abbreviated as dppbz, and their utilization as catalyst for CN bond formation reactions. Reaction of dppbz has been carried out with three different copper(I) sources. While reaction with [Cu(CH3CN)4]ClO4 affords [CuI(dppbz)2]ClO4 (complex 1), that with CuI and CuSCN affords di-copper complexes [{CuI(dppbz)I}2] and [{CuI(dppbz)(SCN)}2] (complexes 2 and 3) respectively. Bulk characterization on the complexes has been done by elemental (C, H, N) analysis, magnetic susceptibility measurement, and spectroscopic (IR, NMR and UV–vis) methods. Crystal structures of all three complexes have been determined. In [CuI(dppbz)2]ClO4, copper(I) is having a highly distorted tetrahedral CuP4 core. In [{CuI(dppbz)I}2] and [{CuI(dppbz)(SCN)}2], the tetrahedral CuP2I2 and CuP2SN cores are relatively less distorted. These copper complexes have been found to serve as efficient catalyst precursors for two types of CN bond formation reactions, viz. hydroamination and click reaction. Hydroamination of aryl alkynes with aryl amines has afforded selectively imine products of a single type (Markownikov product) in good yields under relatively mild condition. However, similar hydroamination with benzyl amines or alkyl amines has afforded selectively anti-Markownikov imine products. Click reaction between aryl alkynes and aryl azides yielding the cycloaddition products has also been brought about successfully with remarkable catalytic efficiency.

Versatile Electroluminescence Color-Tuning Strategy of an Efficient Light-Emitting Electrochemical Cell (LEC) by an Ionic Additive.

The color-tuning strategies of solid-state light-emitting devices (ss-LEDs) are mainly focused on engineering molecular structures. In this paper, for the first time, we developed a facile strategy for tuning the electroluminescence (EL) color from orange to green through the addition of the ionic additive TBAP (tetrabutylammonium perchlorate). To achieve the active ionic emissive compound for use in a light-emitting electrochemical cell (LEC), the neutral biscyclometalated bromo tetrazole iridium(III) [Ir(ppy)2(BrTz)] was exchanged to its cationic complex, [Ir(ppy)2(BrTz-Me)]ClO4 (ppy = 2-phenyl pyridine, BrTz = 4-bromo-2-pyridine tetrazole, BrTz-Me = 4-bromo-2-pyridine methyl tetrazole) with a new synthetic strategy. This method allows employing neutral Ir-cyclometalated complexes, which are ruled out for use in LECs because of their non-ionic behaviors. In the following, an LEC based on the new cationic [Ir(ppy)2(BrTz-Me)]ClO4 as the emissive layer was fabricated between the FTO (fluorine-doped tin oxide) anode and Ga:In alloy cathode without using any additive or polymers, which makes this configuration the simplest ss-LED so far. By adding the ionic additives, the electroluminescence characteristics of [Ir(ppy)2(BrTz-Me)]ClO4 were dramatically increased, including luminance (L) from 162.8 cd/m2 for the device with an additive to 212.9 and 355.9 cd/m2 for devices containing LiTFSI (bis(trifluoromethane)sulfonamide lithium salt) and TBAP, respectively. In particular, when TBAP was added to the [Ir(ppy)2(BrTz-Me)]ClO4 complex, the irradiance was significantly increased from 166.4 to 220.8 μW/cm2 with an efficacy of 1.78 cd/A and external quantum efficiency (EQE) value of 2.14%. The obtained EL results clearly showed that adding TBAP and LiTFSI significantly improved the electroluminescence characteristics and tuned the electroluminescence color.

Photophysical, catalytic, and theoretical investigations of kinetically stable [Cu(2,2′-biquinoline)(PR3)2]+ and [Cu(neocuproine)(PR3)2]+ complexes

Four complexes were synthesized and characterized with the formula [Cu(N^N)(PMePh2)2]ClO4 (4 and 6) or [Cu(N^N)(dppe)]ClO4 (5) and 7){N^N = 2,2′-biquinoline, neocuproine}. Crystal structures of the neocuproine-containing complexes (5 and 7) were obtained and described. The methyldiphenylphosphine-containing complexes are stable in solutions (compared to PPh3) due to: (1) slightly better σ-donation compared to PPh3 and (2) smaller Tolman cone angle of ∼136° (compared to ∼145° in PPh3). In the other hand, [Cu(N^N)(dppe)]ClO4 complexes were demonstrating evidence of forming [Cu(N^N)2]+ in solutions, highlighting the importance of the P-Cu-P angle. The angle P-Cu-P is around 123° in stable complex 5 compared to ∼92° in 7. Absorption spectra of 4 and 5 exhibit low intensity broad shoulder in the visible light domain assigned as MLLCT by computational studies. While [Cu(2,2′-biquinoline)(PPh3)2]+ cation was losing catalytic activity in Castero-Stephens cross-coupling over time as indicated by the low conversion rate, complexes 4 and 5 found to be active and achieved complete conversion of the starting materials.

Synthesis, Molecular and Supramolecular Structure Aspects, and Antimicrobial Activity of the Centrosymmetric [Ag(5-Nitroquinoline)2]ClO4 Complex

The new homoleptic [Ag(5-nitroquinoline)2]ClO4 centrosymmetric complex was synthesized and its structure aspects were investigated. It crystallized in the monoclinic space group C2/c with a = 10.0279(2) Å, b = 13.2295(3) Å, c = 14.7552(3) Å and β = 102.1050(10)° while V = 1913.96(7) Å3 and half molecule as asymmetric formula. The Ag(I) is coordinated with two symmetrically related 5-nitroquinoline ligand units via the heterocyclic nitrogen atom with Ag-N distance of 2.146(6) Å and N1-Ag-N1 angle of 173.0(3)°. The two coordinated 5-nitroquinoline have anti configuration to one another and the perchlorate anion is set freely uncoordinated. The only Ag…O interactions are Ag1…O2 (3.110 Å) and Ag1…O1 (3.189 Å) which occur between the Ag(I) in one complex unit and the O-atoms from the NO2 groups in the neighbouring complex units. Hence, Ag(I) has coordination number 2 and its coordination geometry is slightly bent. Hirshfeld analysis indicated that the O…H (51.1%), C…H (11.8%), H…H (10.8%) and C…C (8.9%) contacts are the most common. Exclusively, the O…H, C…O, N…O, O…O and Ag…O contacts are the only shorter contacts than the vdWs radii sum of the interacting atoms. The studied Ag(I) complex showed good antimicrobial activity. It has comparable antibacterial activity against P. vulgaris (MIC = 9.7 μg/mL) and S. aureus (39.1 μg/mL) to Gentamycin (4.8 and 9.7 μg/mL, respectively) while better antifungal activity against A. fumigatus (MIC = 39.1 μg/mL) than Ketoconazole (156.2 μg/mL).

In Vitro Effect of Copper (I) Complex [Cu(NN1)2](ClO4) on Vibrio harveyi BB170 Biofilm Formation.

Biofilm formation in pathogenic bacteria is an important factor of resistance to antimicrobial treatments, allowing them to survive for a long time in their hosts. In the search for new antibiofilm agents, in this work we report the activity of a copper (I) complex, [Cu(NN1)2]ClO4, synthesized with Cu (I) and NN1, an imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one, a derivate of natural compound coumarin. The antibacterial and antibiofilm capacity was evaluated in Vibrio harveyi BB170 used as model bacteria. Antibacterial activity was measured in vitro by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and half-maximal inhibitory concentration (IC50) determination. Antibiofilm capacity of copper (I) complex was analyzed by different concentrations of IC50 values. The results showed that the sub-IC50 concentration, 12.6 µg/mL of the copper (I) complex, was able to reduce biofilm formation by more than 75%, and bacterial viability was reduced by 50%. Inverted and confocal laser scanning microscopy showed that the [Cu(NN1)2]ClO4 complex affected the biofilm structure. Therefore, the copper (I) complex is effective as an antibiofilm compound in V. harveyi BB170.

Synthesis, crystal structure, and theoretical studies of a macrocyclic silver(I) complex of imino-pyridyl Schiff base ligand

The synthesis and characterization of an imino-pyridyl ligand N,N'-(butane-1,4-diyl)bis(1-(pyridin-2-yl)methanimine) (L) and its Ag(I)ClO4 complex (I) by various spectroscopic techniques and elemental analyses is presented in this study. X-ray single crystal structure of complex I revealed that in complex I, each Ag(I) ion is tetra coordinated with two pyridine N-atoms and two imine N-atoms of the ligand L, forming a macrocyclic dimeric Ag(I) grid. In the macrocyclic dimer complex I, Ag-Ag separation along the chain is 5.318 Å. The Ag-Npy average distance is 2.396 Å and that of the Ag-Nim is 2.257 Å. The macrocyclic dimer complex I is supramolecularly arranged by π-stacking interactions. Computational, Hirshfeld surface analysis and photophysical studies on ligand L and complex I have also been performed. Crystal data for C32H36Ag2Cl2N8O8 (M =947.33 g/mol): Triclinic, space group P-1 (no. 2), a = 9.1714(12) Å, b = 10.4373(14) Å, c = 10.8297(14) Å, α = 112.317(3)°, β = 91.391(3)°, γ = 92.353(3)°, V = 957.3(2) Å3, Z = 1, T = 293.15 K, μ(MoKα) = 1.220 mm-1, Dcalc = 1.643 g/cm3, 10248 reflections measured (4.07° ≤ 2Θ ≤ 53.098°), 3966 unique (Rint = 0.0280, Rsigma = 0.0331) which were used in all calculations. The final R1 was 0.0722 (I > 2σ(I)) and wR2 was 0.2229 (all data).

Synthesis, spectral and structural studies on NiS2PN and NiS2P2 chromophores and use of Ni(II) dithiocarbamate to synthesize nickel sulfide and nickel oxide for photodegradation of dyes

The substitution of one of the dithiocarbamate ligands in homoleptic [Ni(dtc)2] (1) complex (dtc = N,N-di(4-methoxybenzyl)dithiocarbamate) with the phosphine ligands gave heteroleptic [Ni(dtc)(PPh3)(NCS)] (2), [Ni(dtc)(PPh3)2] ClO4 (3) and [(dtc)(dppe)] ClO4 (4) complexes. The complexes 2–4 were characterized by elemental analysis, spectroscopy and single crystal X-ray diffraction analysis. Single crystal X-ray diffraction studies revealed that 2–4 adopt distorted square planar geometry. Non-covalent interactions in 2–4 were quantified using Hirshfeld surface analysis. The study of single crystal X-ray diffraction of 2–4 shows that various interactions such as C–H⋯π (chelate), C–H⋯π, C–H⋯O and C–H⋯S among molecules of complexes 2–4, participate in cooperative way to stabilize the supramolecular interactions. DFT calculations were used to determine the electronic structure and properties of 2. The HOMO-LUMO energy difference (2.7445 eV) is observed to be small which shows the low kinetic stability of 2. Nanoparticles of nickel sulfide and nickel oxide were successfully synthesized by solvothermal and thermal decomposition of 1, respectively and characterized by powder X-ray diffraction (PXRD), High Resolution Scanning Electron Microscopy (HRSEM), Energy Dispersive Spectroscopy (EDS) and UV Diffuse Reflectance Spectroscopy (UV-DRS). The photocatalytic activity of both nanoparticles was investigated for degradation of methylene blue and rhodamine 6G under UV irradiation. The results revealed that the nickel oxide has higher photocatalytic activity than nickel sulfide.

Synthesis, structure and biological activity of zinc(II) pincer complexes with 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine

The reaction of 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-methoxy-1,3,5-triazine (BPT) pincer ligand with Zn(NO3)2 and Zn(ClO4)2·6H2O/HCl yielded, [Zn(BPT)(NO3)2] (2), and [Zn(BPT)(H2O)Cl]ClO4 (3) complexes, respectively. However, zinc(II) chloride with BPT involved CN rupture and formed instead [Zn(DMP)2Cl2] (1) complex (DMP = 3,5-dimethylpyrazole). The structures of all complexes were confirmed by single crystal X-ray structure and NMR analyses. The intermolecular interactions included in the molecular packing of the complex units were analyzed using Hirshfeld analysis. Bond topological parameters were utilized to investigate the nature and strength of the Zn-N, Zn-Cl and Zn-O coordination interactions. The antimicrobial profile of the Zn(II) complexes were examined against Gram-positive and Gram-negative bacteria as well as the fungus C. albicans. The two pincer complexes (2 and 3) were found to be good antibacterial and antifungal agents while the ligand (BPT) was not active at the applied concentration. Also, the nitrato (2) and perchlorate (3) Zn(II) complexes are more potent antimicrobial agents than complex 1.

Mixed ligand Cu(II) complexes of an unsymmetrical Schiff base ligand and N-donor heterocyclic co-ligands: Investigation of the effect of co-ligand on the antibacterial properties

In this study, two new and one previously reported mixed ligand Cu(II) complexes were synthesized and characterized. The complexes have general formula [Cu(L1)(L2)]ClO4 in which L1 is an NN′O type unsymmetrical tridentate Schiff base ligand and L2 is an N-donor heterocyclic ligand, i.e. 2,2′-bipyridine in complex (2), 4,4′-di-t-butyl-2,2′-bipyridine in (3) and 1,10-phenanthroline in (4). The Schiff base ligand is the mono-condensed form of the reaction between ethylenediamine with salicylaldehyde. The complexes were characterized by IR and UV–Vis spectroscopy, as well as elemental analyses. Crystal structures of two of the complexes (2 and 3) were also obtained by X-ray crystallography. The complexes were tested as antibacterial agents against two gram positive and two gram negative human pathogenic bacteria, i.e. Staphylococcus aureus (Gram positive), Bacillus subtilis (Gram positive), Salmonella typhi (Gram negative), and Escherichia coli (Gram negative). The precursor [Cu(L1)(py)]ClO4 complex (1) was also tested for comparison. The results showed that the complexes (1), (2) and (3) were moderately active against the studied bacteria, while complex (4) with 1,10-phenanthroline co-ligand showed very good antibacterial activity.

Highly-efficient N-arylation of imidazole catalyzed by Cu(II) complexes with quaternary ammonium-functionalized 2-acetylpyridine acylhydrazone

The reaction of (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium-chloride (HLCl) with copper(II) perchlorate led to mononuclear [CuLCl]ClO4 complex (1). The same reaction with excess of sodium azide gives dinuclear azido double end-on bridged Cu(II) complex [Cu2L2(μ-1,1-N3)2](ClO4)2 (2). In both complexes hydrazone ligand is NNO coordinated in monodeprotonated formally neutral zwitter-ionic form. Complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Variable‐temperature magnetic susceptibility measurements for dinuclear Cu(II) complex showed intra-dimer ferromagnetic coupling between Cu(II) ions (J = 7.4 cm−1). DFT-BS calculations provided explanation for magnetic properties of dinuclear Cu(II) complex. Both complexes were shown to highly efficiently catalyze the N-arylation of imidazole and benzimidazole with electron-poor or electron-rich aryl iodides, under user-friendly and sustainable conditions.

X-ray Structure and DFT Studies of a New Square Planar Silver(I) Complex of Ketene S,S-Dithioacetal Ligand

The [AgL2]ClO4 complex, where L is ketene S,S-dithioacetal type ligand, is synthesized and characterized using elemental analysis, different spectroscopic techniques (FTIR and NMR) and single crystal X-ray diffraction (SC-XRD). The Ag-atom is coordinated by two oxygen and two sulfur atoms of both bidentate ligands resulting in a distorted square planar environment augmented by two weak contacts with two oxygen atoms from the perchlorate anion. The H⋯H (42.0%), O⋯H (29.7%), C⋯H (10.8%) and S⋯H (11.7%) intermolecular contacts were quantified using Hirshfeld analysis. The PBEPBE and WB97XD methods are the best to predict the Ag–S and Ag–O(L) distances. Natural bond orbital (NBO) analysis showed that each ligand (L) transferred 0.1507 e (exp. 0.1715 e) to Ag-atom while the perchlorate anion lost 0.1748 e (exp. 0.1481 e) to silver {0.5227 e (exp. 0.5088 e)}. The structure aspects of the newly synthesized square planar [AgL2]ClO4 complex, where L is ketene S,S-dithioacetal ligand, were analyzed using different spectroscopic techniques (FT-IR, NMR) and X-ray single crystal structure combined with DFT calculations.

Square planar versus square pyramidal copper(II) complexes containing N3O moiety: Synthesis, structural characterization, kinetic and catalytic mimicking activity

In quest of copper complexes having [CuN3O] cores, [Cu(phen)(l–Val)(H2O)]NO3 (1) and [Cu(bpy)(l–Val)]ClO4 (2) complexes have been synthesized and structurally characterized (phen = 1,10–phenanthroline; bpy = 2,2′–bipyridine). Complex 1 possesses a distorted square-pyramidal, whereas 2 has a distorted square-planar coordination geometry. Structures of 1 and 2 have supramolecular networks formed via inter- and intra-molecular hydrogen bonding interactions. The kinetics and mechanism of ligand substitution of 1 and 2 by thiourea (TU) were studied in detail and showed a biphasic process in which an initial fast reaction is followed by a slower one. The activation parameters for the fast reaction: ΔH# = 68 ± 4 and 73 ± 5 kJ mol−1, ΔS# = 43 ± 10 and 54 ± 9 J K−1 mol−1 for 1 and 2, respectively, supports a dissociative substitution mechanism. Whereas for the slow reaction: ΔH# = 33 ± 6 and 43 ± 3 kJ mol−1, ΔS# = −77 ± 10 and −56 ± 9 J K−1 mol−1 for 1 and 2, respectively, support an associative substitution mechanism. It is concluded from the activation parameters that the difference in structure does not affect the mechanism. Complexes 1 and 2 have also been evaluated as functional models for the catechol oxidase enzyme and phenoxazinone synthase. The model complexes 1 and 2 show catecholase activity of Kcat = 10.9 × 103 and 11.4 × 103 h−1 and phenoxazinone synthase activity of Kcat = 2.1 × 103 and 4.3 × 103 h−1, respectively. Compared to the enzyme itself (Kcat = 8.3 h−1), the model complexes 1 and 2 are promising candidates as functional mimics for catechol oxidase and phenoxazinone synthase.

Effects of non-covalent interactions on the electronic and electrochemical properties of Cu(i) biquinoline complexes

A Cu(i) complex {[CuI(biq)2]ClO4-biq} with biq = 2,2'-biquinoline was prepared, fully characterized and its properties compared with those of the well-known [CuI(biq)2]ClO4 complex. The crystal structures were obtained for both complexes (crystal structure for [CuI(biq)2]ClO4 has not been previously reported). Complex [CuI(biq)2]ClO4 crystallizes as a racemate where each enantiomer has a different τ4 value while compound {[CuI(biq)2]ClO4-biq} crystallizes as a non-chiral supramolecular aggregate with an uncoordinated biq molecule forming a π-π stacking interaction with a coordinated biq. 1H-NMR spectroscopy in non-coordinating solvents reveals that structures in solution are similar to those in the solid phase, confirming the presence of a supramolecular arrangement for compound {[CuI(biq)2]ClO4-biq}. The stability of the non-covalent aggregate in solution of {[CuI(biq)2]ClO4-biq} causes significant differences between the spectroscopic and electrochemical properties of {[CuI(biq)2]ClO4-biq} and [CuI(biq)2]ClO4.

Experimental and theoretical structural determination, spectroscopy and electrochemistry of cobalt (III) Schiff base complexes: immobilization of complexes onto Montmorillonite-K10 nanoclay

The [Co(5-XSalen)(PEt3)(H2O)]ClO4 (where Salen = bis(salicylaldehyde)1,2-ethylenediamine and X = H, MeO, NO2, Br) complexes were successfully synthesized and characterized by different techniques such as FT-IR, UV–Vis, 1HNMR, 13CNMR and 31PNMR. The coordination geometry of the [Co(5-BrSalen)(PEt3)(H2O)]ClO4 complex was determined by X-ray crystallography. The complex has six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base form the equatorial plane. The cyclovoltammetry was used to study the electrochemical properties of cobalt complexes, and the results reveal the anodic peak potential becomes more positive in order to MeO < H < Br < NO2. DFT calculations were also done to investigate structures, electronic spectra and infrared spectra of the complexes. The synthesized complexes [Co(Salen)(PEt3)(H2O)]ClO4, [Co(Salen)(PBu3)(H2O)]ClO4 and [Co(5-NO2Salen)(PEt3)(H2O)]ClO4 were incorporated within Montmorillonite-K10 (MMT) nanoclay. Furthermore, structural, thermal and morphological properties of the prepared nanohybrids were verified by FT-IR, XRD, TGA-DTG, EDX, SEM and TEM techniques. XRD results of the new nanohybrid materials elucidate that the Schiff base complexes were placed at the most outerlayer spaces of MMT clay.

Synthesis, X-ray structure and topology (AIM and Hirshfeld) analyses of the new square planar [Ag(pyridine-2-aldoxime)2]ClO4 complex; A comparative study with its nitrato analogue

The new homoleptic square planar complex [AgL2]ClO4·H2O; 1, where L is pyridine-2-aldoxime, is synthesized and characterized using elemental analysis, FTIR and NMR spectra as well as X-ray single crystal structure analysis. The ligand (L) acts as a bidentate ligand via the pyridine and oxime N-atoms while the perchlorate anion is not coordinated to the silver atom. The crystal structure of 1 is characterized by one-dimensional infinite hydrogen bond network with backbone build up by hydrogen bridge interactions between the water molecules, the OH groups of the aldoxime and the perchlorate anions. The structure of 1 is optimized using eight DFT methods. The B97D/def2-TZVP and PBEPBE/def2-TZVP are the best to predict the AgN/AgO distances and the coordination geometry around Ag(I) ion, respectively. Atoms in molecules (AIM) and Hirshfeld topology analyses were used to describe the AgN/AgO bonding nature and the possible intermolecular interactions, respectively, in comparison with the nitrato analogue [AgL(NO3)]; 2. The O⋯H, H⋯H, C⋯C and H⋯C are the most common intermolecular interactions occurred in both complexes. Only complex 2 showed significant Ag⋯O (2.720–2.731 Å) intermolecular interactions. AIM and NBO analyses explained that the ClO4− anion is weakly interacting with Ag(I) in 1 while the NO3− is coordinated via one of its O-atoms in 2.

Synthesis, structural analyses and antimicrobial activity of the water soluble 1D coordination polymer [Ag(3-aminopyridine)]ClO4

The synthesis, characterization and molecular structure aspects of the [Ag(3-aminopyridine)]ClO4 coordination polymer have been presented. Single crystal X-ray diffraction (SC-XRD) analysis showed that the asymmetric unit consists of two Ag, one 3-aminopyridine (3APy) and one ionic perchlorate anion. The 3-aminpyridine (3APy) acts as a bridged ligand connecting the Ag-atoms via the amine and pyridine ring N-atoms leading to the formation of 1D coordination polymer. The perchlorate anion connects the 1D chains via a complicated set of NH⋯O and CH⋯O hydrogen bonding interactions. Strong FTIR spectral bands at 1143.1, 1116.7 and 1085.6 cm−1 and a weak band at 932.9 cm−1 revealed the ionic character of the complex. Single point DFT calculations combined with atoms in molecules (AIM) and natural bond orbital (NBO) analyses indicated stronger AgN(py) than AgN(NH2) interaction. The former has more covalent character according to the AIM topological parameters. The Ag⋯O interactions are weak and are mainly affected by dispersion interactions. Of the six DFT methods used for geometry optimizations, the TPSSTPSS then PBEPBE are the most powerful DFT methods to predict the AgN distances. Effect of methods on the frontier molecular orbitals energies and shapes are also presented. Preliminary antimicrobial studies showed that the [Ag(3APy)]ClO4 complex has more activity against all the studied microorganisms than the free 3APy.

The design of synthetic superoxide dismutase mimetics: seven-coordinate water soluble manganese(ii) and iron(ii) complexes and their superoxide dismutase-like activity studies.

Bio-inspired manganese [Mn(N5Py)(H2O)(CH3OH)](ClO4)2 (1) and iron [Fe(N5Py)(H2O)(ClO4)]ClO4 (2) complexes derived from a pentadentate ligand (N5Py = 2,6-bis((E)-1-phenyl-2-(pyridin-2-ylmethylene)hydrazinyl)pyridine) framework containing a N5 binding motif were synthesized and characterized using different spectroscopic methods. The molecular structures of complexes 1 and 2 were determined by X-ray crystallography. These complexes were found to be stable under physiological conditions and exhibited an excellent superoxide dismutase (SOD) activity. The SOD activity was determined by a xanthine-xanthine oxidase-nitro blue tetrazolium assay and the IC50 values were determined to be 1.53 and 2.09 μM, respectively.

Investigation of easy-plane magnetic anisotropy in P-ligand square-pyramidal CoII single ion magnets.

In this work we report two pentacoordinated CoII-P4X1 Single Ion Magnets (SIMs) based on P-donor ligands. The tetradentate ligand tris[2-(diphenylphosphino)ethyl]phosphine allows the obtention of the isostructural square pyramidal [Co(PP3)Cl]·ClO4 (1) and [Co(PP3)Br]·ClO4 (2) complexes. Consistent theoretical and experimental studies indicate that these complexes have a high spin (S = 3/2) ground state and suggest that the relaxation dynamics is governed by ground state quantum tunneling, whereas its temperature dependence is directed by optical or acoustic Raman processes.