The synthesis and characterization of four new iron(III) coordination compounds with saltrien-like hexadentate Schiff base ligands Ln, prepared by condensation between triethylenetetramine and 2-hydroxy-3,5-dimethylbenzophenone (L1, C1-C3) or 2-hydroxy-5-methoxybenzophenone (L2, C4), are reported. The complexes [Fe(Ln)]X·mCH3CN (X = SeCN- for C1 and C4, SCN- for C2 and BPh4- for C3, m = 0 for C3, m = 1 for C1 and C4, m = 2 for C2) were structurally characterized, and their spin-crossover (SCO) was monitored by magnetic measurements, X-ray powder diffraction analysis, and EPR spectroscopy. Intermolecular interactions relevant to SCO were analyzed through Hirshfeld surface maps and QT-AIM calculations. All compounds exhibit SCO above room temperature in their solvated forms, and ab initio calculations were employed to probe their electronic structures. While the computed 2T2g-6A1g gaps and 10Dq energies are consistent across the whole series, the experimental T1/2 values do not directly reflect these energy differences. Instead, SCO is predominantly controlled by crystal packing effects, including intermolecular connectivity, internal pressure, lattice rigidity, and solvation. Upon heating, solvent removal in C1 and C2 shifts their SCO to below room-temperature. The desolvated compounds C1d and C2d exhibit sharp SCO with wide hysteresis, while C2d additionally features a second gradual step (C1d: T1/2 = 82 K/166 K; C2d: T(1)1/2 = 170 K/153 K, T(2)1/2 = 110 K). Furthermore, both compounds are LIESST active upon blue light irradiation (T(LIESST)=57 K for C1d and 36 K for C2d). These results underscore the crucial role of ligand flexibility, solvation, and intermolecular interactions on SCO and highlight the potential of these iron(III) complexes in molecular switching applications.

Six novel copper(II) compounds with derivatives of methylsalicylate (MeSal-) and methoxysalicylate anions (MeOSal-) and 2-(hydroxymethyl)benzimidazole (2-MeBzim), were prepared and characterized by elemental analysis, X-ray analysis IR, UV-Vis and EPR spectroscopy. The synthesis in the presence of 3-methylsalicylate anion led to formation of two complexes with same composition [Cu(3-MeSal)2(2-MeBzim)2] (1a and 1b) which provide a fortunate case of reproducible conformational polymorphism/isomerism. Using state-of-the-art metadynamic computational simulations, the hypothesis that their formation is due to the use of different solvents has been verified.

Two novel and two previously prepared and published copper(II) complexes were synthetized using Xbenzoic acids (where X = 2-NO2, 2-Cl, 2-Br, 2-I) and 4-pyridylmethanol (4-PM): [Cu(2-NO2bz)2(4-PM)2(H2O)] 1, [Cu(2-Clbz)2(4-PM)2(H2O)] 2, [Cu(2-Brbz)2(4-PM)2(H2O)] 3 and [Cu(2-Ibz)2(4-PM)2(H2O)] 4. The structures of the newly prepared complexes 1 and 4 were determined by single-crystal X-ray analysis, and the intermolecular interactions were studied by Hirshfeld surface analysis for all complexes. All the complexes were characterized by IR, UV-vis and EPR spectroscopy (in solid-state and DMSO solution) and their redox properties were deter-mined by cyclic voltammetry. The interaction of complexes 1-4 with calf-thymus DNA was monitored by diverse techniques (UV-vis spectroscopy, viscosity measurements) suggesting intercalation as the most possible mode of binding (Kb = 1.15 x 105-3.44 x 106 M-1). The cytotoxic effects of copper(II) complexes on lung carcinoma cells were determined by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] colorimetric technique. Furthermore, their SOD and catechol oxidase mimetic activity were studied.

The new mononuclear manganese(II) complex with chlorido-substituted hexadentate Schiff base (H23,5-2Cl-sal-N(1,5,8,12) = N,N '-Bis[3-(3,5-dichloridosalicylideneamino)propyl]-ethane-1,2-diamine) were synthesized and its crystal structure was solved using single-crystal X-ray diffraction. The complex crystallizes in a triclinic system with a P1 space group. Manganese(II) central atom is coordinated by two atoms of oxygen and four atoms of nitrogen of the Schiff base. The supramolecular structure of the complex and the intermolecular interactions were analyzed using Hirshfeld surface analysis. The complex was characterized by UV-vis and infrared spectra, and the presence of a high-spin Mn(II) state (S = 5/2) was revealed by EPR spectroscopy in the solid state.

The synthesis of six new copper(II) nitrobenzoate complexes with N -methylnicotinamide, used as an auxiliary ligand for a supramolecular interaction study, is reported. Crystal structures of six novel compounds [Cu(2-NO 2 bz) 2 (mna) 2 (H 2 O) 2 ] ( 1 ), [Cu(2-NO 2 bz) 2 (mna) 2 (H 2 O) 2 ]∙2H 2 O ( 2 ), [Cu(3-NO 2 bz) 2 (mna) 2 (H 2 O) 2 ] ( 3 ), [Cu(3,5-(NO 2 ) 2 bz) 2 (mna) 2 (H 2 O) 2 ]∙2H 2 O ( 4 ), [Cu(4-NO 2 bz) 2 (mna) 2 (H 2 O) 2 ]∙2(4-NO 2 bzH) ( 5 ) and [Cu(3,5-(NO 2 ) 2 bz) 2 (mna)(H 2 O) 3 ] ( 6 ) (mna = N -methylnicotinamide, 2-NO 2 bz = 2-nitrobenzoate, 3-NO 2 bz = 3-nitrobenzoate, 4-NO 2 bz = 4-nitrobenzoate, 3,5-(NO 2 ) 2 bz = 3,5-dinitrobenzoate) were determined by X-ray analysis. Compounds 1 – 6 are mononuclear with a tetragonal-bipyramidal geometry around the Cu 2+ ion. The molecules of the studied complexes are mostly linked by a combination of N–H…O and O–H…O hydrogen bonds between N -methylnicotinamide and water molecules into supramolecular hydrogen-bonded coordination chains and networks. Intermolecular interactions in the supramolecular structures were also studied using Hirshfeld surface analysis. In addition, the complexes 1–6 have been characterised by elemental analysis, IR, UV–Vis and EPR spectroscopy. Density functional theory calculations were performed in order to reproduce the EPR magnetic parameters. DFT calculations of the EPR parameters show a good agreement with the experimental results.

In this work, attention is focused on the non-essential amino acid L-Tyrosine (TYR) hydroxylated to L-DOPA, which is the precursor to the neurotransmitters dopamine, noradrenaline (norepinephrine; NE) and adrenaline (epinephrine; EP) known as catecholamines and their interactions with redox-active Cu(II). Catecholamines have multiple functions in biological systems, including the regulation of the central nervous system, and free (unbound) redox metal ions are present in many diseases with disturbed metal homeostasis. The interaction between catecholamines and Cu(II) has been studied by means of Electron Paramagnetic Resonance spectroscopy (EPR), EPR spin trapping and UV-vis spectroscopy. The obtained spectroscopic results are supported by Density Functional Theory calculations. Only minor qualitative and quantitative changes in the UV-vis spectra of all the studied compounds have been observed following their interactions with Cu(II) ions. The low-temperature EPR spectra were more convincing and confirmed the interaction between Cu(II) ions and all the studied compounds, involving hydroxyl groups and amino nitrogens. The use of an ABTS assay revealed that the compounds under study possessed radical-scavenging activities against ABTS•+ in the order TYR < EP < DA < NE~L-DOPA. The neurotransmitters DA, NE and EP, following their interaction with Cu(II), exhibit the ability to (partially) reduce Cu(II) to Cu(I) species which was confirmed using the Cu(I) specific chelator neocuproine. EPR spin-trapping experiments revealed the suppressed formation of hydroxyl radicals (•OH) in a copper(II) catalyzed Fenton-like system in the presence of catecholamines. Only in the case of EP was autooxidation in a stock solution observed. Furthermore, the oxidation of EP is enhanced in the presence of Cu(II) ions. In conclusion, it has been confirmed that the oxidation of catecholamines in the presence of copper promotes the redox cycling process, resulting in the formation of ROS, which may, in turn, cause damage to neuronal systems.

Three new methylsalicylatocopper and four methylbenzoatocopper complexes with 2-(hydroxymethyl)benz-imidazole with structures, [Cu(3-MeSal)2(2-MeBzim)2]center dot 2H2O (1), [Cu(4-MeSal)2(2-MeBzim)2] (2), [Cu(5-MeSal)2(2-MeBzim)2]center dot 2H2O (3), [Cu(2-MeBenz)2(2-MeBzim)2] (4), [Cu(3-MeBenz)2(2-MeBzim)2] (5), [Cu(4-MeBenz)2(2-MeBzim)2] (6), [Cu(4-MeBenz)2(2-MeBzim)2]center dot EtOH (7), where 3-MeSal- = 3-methylsalicylate, 4- MeSal- =4-methylsalicylate, 5-MeSal- = 5-methylsalicylate, 2-MeBenz- = 2-methylbenzoate, 3-MeBenz- = 3-methylbenzoate and 4-MeBenz- = 4-methylbenzoate anion and 2-MeBzim = 2-(hydroxymethyl)benzimidazole were synthesized. Solid-state complexes were characterized by diffraction methods, elemental analysis, UV/VIS, IR, and EPR measurements. Hirshfeld surface analyses were made for crystal structures of all complexes. Co-ordination polyhedron around the copper central atom is elongated tetragonal bipyramid and two molecules of 2-(hydroxymethyl)benzimidazole and two anions of methylsalicylate or methylbenzoate are bonded in a mon-odentate way to the copper center. For six prepared complexes the antimicrobial and acaricidal activities have been studied. Antifungal activity has been studies on fungal species Aspergillus fumigatus, Microsporum gypseum, and Candida albicans. Antibacterial activity has been studied on bacterial strains Escherichia coli, and Staphylo-coccus aureus, and acaricidal activity was determined on Phytoseiulus perimilis. Complexes 1, 2 and 3 almost entirely inhibited the growth of S. aureus and complexes 1, 5 and 6 practically completely suppressed the growth of yeast strain C. albicans.

Through the reaction of copper(II) acetate with nicotinamide (pyridine-3-carboxylic acid amide, niacinamide) and some derivatives of N-phenylanthranilic acid (fenamates), seven new mixed-ligand copper(II) compounds were isolated: [Cu(tolf-O)(tolf-O,O')nia-N)(2)(EtOH)] (1), [Cu(tolf-O)(tolf-O,O')(nia-N)(2)(MeOH)] (2), [Cu(meclfO)(meclf-O,O')(nia-N)(2)(EtOH)] (3), [Cu(meclf-O)(meclf-O,O')(nia-N)(2)(MeOH)] (4), [Cu(meclf-O)(meclf-O,O') (nia-N)(2)(ACN)] (5), [Cu(mef-O)(mef-O,O')(nia-N)(2)(EtOH)] (6) and [Cu(mef-O)(mef-O,O')(nia-N)(2)(ACN)] (7) containing a molecule of relevant solvent as ligand in their primary crystal structure (tolf = tolfenamate, meclf = meclofenamate, mef = mefenamate, nia = nicotinamide, EtOH = ethanol, MeOH = methanol, ACN = acetonitrile). The structures of the complexes were determined by single-crystal X-ray analysis. The intermolecular interactions were studied by Hirshfeld surface analysis. The complexes were characterized by IR, UV-vis and EPR spectroscopy and their redox properties were determined by cyclic voltammetry. The interaction of the complexes with bovine serum albumin was studied by fluorescence emission spectroscopy and the albumin-binding constants of the compounds were calculated. The interaction of the complexes with calf-thymus DNA was monitored by diverse techniques (UV-vis spectroscopy, cyclic voltammetry, viscosity measurements) suggesting intercalation as the most possible mode of binding. DNA-competitive studies of the complexes with ethidium bromide were monitored by fluorescence emission spectroscopy. The cytotoxic effects of copper(II) complexes on lung carcinoma cells and healthy cells were determined by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] colorimetric technique.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Herein, two unsaturated macrocyclic copper(II) complexes, namely, [CuLA(ClO4)(2)] (1) [L-A = 3,14-dimethyl-2,6,13,17-diazadiazoniatricyclo[16.4.0.0(7,12)]docosa-2,13-diene) and [CuLB(ClO4)]ClO4 (2) (L-B = 3,14-diethyl-2,6,13,17-diazadiazoniatricyclo[16.4.0.0(7,12)]docosa-2,13-diene), were synthesized. The complexes were characterized by single-crystal X-ray determination and physico-chemical methods. Complex 1 crystallized in the monoclinic P2(1)/n space group with Z = 2, while complex 2 crystallized in the monoclinic P2(1)/c space group with Z = 4. The asymmetric unit of complex 1 contained one half of the [CuLA](2+) cation and a single perchlorate anion, whereas complex 2 comprised a single [CuLB(ClO4)](+) cation and one doubly disordered perchlorate anion. The Cu(II) ion in complex 1 adopted a six-coordinated tetragonal geometry coordinated by four N atoms of the macrocyclic ligand L-A [Cu-N-amine 2.000 (2) angstrom and Cu-N-imine 1.962 (3) angstrom] and two axial perchlorate O atoms [Cu-O 2.6736 (4) angstrom], while the Cu(II) ion in complex 2 adopted a five-coordinated square pyramidal geometry coordinated by four N atoms of L-B [mean Cu-N-amine 1.9892 (17) angstrom and Cu-N-imine 1.9915 (18) angstrom] and an apical perchlorate O-atom [Cu-O 2.6318 (5) angstrom]. The crystals were stabilized by hydrogen bonds involving the secondary amine N-H groups of the macrocycles and O atoms of the perchlorate groups. Hirshfeld surface analysis with 2D fingerprint plots revealed that the H center dot center dot center dot H and O center dot center dot center dot H interactions in both complexes 1 and 2 were the main intermolecular interactions. (C) 2021 Elsevier B.V. All rights reserved.

Single crystals of 3,14-dimethyl-2,6,13,17-tetraazoniatricyclo(16.4.0.07,12)docosane tetrachloride tetrahydrate compound, [C20H44N4]Cl4·4H2O (1), were obtained by a novel synthetic route and characterized by elemental analysis and X-ray diffraction. The synthesized compound crystallized in the monoclinic space group P21/n with two molecules of compound 1 in the unit cell [a = 7.5548(3) Å, b = 23.1838(8) Å, c = 8.3101(4) Å; β = 103.390(3)º]. The asymmetric unit contains half a centrosymmetric macrocyclic cation, two chloride anions and two water molecules. The organic [C20H44N4]4+ fragment of 1 adopts an exodentate [3,4,3,4]-D conformation. The C–C and N–C bond lengths of the macrocyclic tetracation range 1.525(3)-1.540(3) Å and 1.505(3)-1.519(3) Å, respectively. A three-dimensional hydrogen bonding network provides crystal cohesion through O–H···Cl, N–H···Cl and N–H···O interactions between organic cations, chloride anions and water molecules. The functional groups present in the crystal were studied by Fourier-transform infrared spectroscopy and Raman spectroscopy. The Hirshfeld surface analysis and 2D fingerprint plots revealed that the crystal packing in 1 is dominated by H···H, Cl···H/H···Cl and O···H/H···O contacts.

Three new monomeric benzoatocopper(II) complexes [Cu(3-MeObz)(2)(4-PM)(2)] (1), [Cu(3-Mebz)(2)(4-PM)(2)] (2) and [Cu(4-mebz)2(4-PM)(2)] (3), two polymers [Cu-2(2-Mebz)(4)(4-PM)](n) (4) and [Cu-2(3-Mebz)(4)(4-PM)](n) (5), and the dimeric complex [Cu-2(2-Fbz)(4)(4-PM)(2)] (6) (where 4-PM = 4-pyridylmethanol, 2-Fbz = 2-fluorobenzoate anion, 3-MeObz = 3-methoxy-benzoate anion and x-Mebz = 2-,3- or 4-methylbenzoate) have been synthesized and characterized by elemental analysis as well as by single-crystal diffraction. All the complexes have been studied by infrared, UV-vis and EPR spectroscopy. The neutral ligand 4-PM acts as a terminal ligand in 1-3 and 6, and as a bridging ligand in 4 and 5. The structural motives are evident in the EPR spectra, which have shown axial symmetric features for 1-3, whilst the polymers as well as the dimer (4-6) have exhibited an acetate-type feature. The monomeric complex molecules of 1-3 and the dimeric molecules of 6 are linked by terminal 4-PM H-bonds to create 2D supramolecular square-grid hydrogen-bonded networks. On the other hand, the 1D polymeric chains of 4 are linked into a 2D supramolecular network, while two coordination chains of 5 come together to generate a ladder type double chain. (C) 2021 Elsevier Ltd. All rights reserved.

A novel oxalato-bridged trinuclear heterometallic complex, cis-[Cr(cyc b)(mu-1,2,3,4-ox)ZnCl2(mu-1,2,3-ox) Cr(cyc b)]ZnCl4 center dot H2O (1) (cyc b = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; C16H36N4, ox = oxalate; C2O42-), was prepared and its structure was determined by single-crystal X-ray diffraction analysis at 100 K. Complex 1 crystallizes in the orthorhombic system space group Pca2(1), with a = 31.702(6), b = 9.087(2), c = 17.677(4) angstrom, and Z = 4. The two [Cr(cyc b)](3+) units are bridged by the central Zn(II) atom through the oxalato groups, which present bis-bidentate (mu-1,2,3,4-ox) and bidentate-monodentate (mu-1,2,3-ox) modes. Each Cr(III) ion is coordinated by four N atoms from the cyc b ligand and two O atoms of the oxalato ligand in cis-V conformation. The central Zn(II) ion is coordinated in a distorted trigonal-bipyramidal geometry formed by two Cl atoms and two O atoms from mu-1,2,3,4-ox and one O atom from mu-1,2,3-ox. However, the ZnCl42- anion and the uncoordinated water molecule remain outside the coordination sphere. Infrared, UV-visible, and electron paramagnetic resonance spectroscopic analyses confirmed the structural data. (C) 2020 Elsevier B.V. All rights reserved.

The crystal and molecular structure of copper(II) 2-chloronicotinate (2-Clnic) of the composition [Cu(2-Clnic)2(pia)2] (pia = Picolinamide) (1), [Cu(2-Clnic)2(nia)2] (nia = Nicotinamide) (2), [Cu(2-Clnic)2(nia)2(H2O)]·H2O (3), [Cu(2-Clnic)2(mna)2(H2O)2] (mna = N-methylnicotinamide) (4), [Cu(2-Clnic)2(2 pm)2] (2 pm = 2-Pyridylmethanol) (5), and [Cu(2-Clnic)2(4 pm)2(H2O)2]·2H2O (4 pm = 4-Pyridylmethanol) (6) were determined by single-crystal X-ray analysis. Crystal structures of the respective complexes are monomeric with a different composition of coordination sphere about Cu(II) atom. The arrangement about Cu(II) in all coordination compounds are pseudooctahedral trans-coordinated, where carboxylic groups are bidentate (2,3) or monodentate (1,3–6) coordinated to atom copper. The molecules of all compounds are connected by strong N–H···O, N–H···N and/or O–H···O hydrogen bonds. EPR spectra of powder complexes 1–6 were measured and computer-simulated.

Six new benzoatocopper(II) complexes with 4-pyridylmethanol (abbreviated as 4-PM) as an N,O-bridging ligand have been prepared and characterized by single-crystal X-ray analysis: [Cu(4-MeOBz)2(µ-4-PM)(4-PM)]n(1), [Cu(3,5-(NO2)2Bz)2(μ-4-PM)(4-PM)]n(2), [Cu(4-MeSal)2(µ-4-PM)2]n(3), [Cu(5-MeSal)2(µ-4-PM)2]n(4), [Cu(3-NO2Bz)2(μ-4-PM)2)]n (5) and [Cu(4-NO2Bz)2(μ-4-PM)2)]n(6) (where 4-PM = 4-pyridylmethanol, MeOBz = methoxybenzoate, MeSal = methylsalicylate, NO2Bz = nitrobenzoate). All these complexes have been characterized by Elemental analysis, IR spectroscopy, EPR spectroscopy. Spectral properties are in good agreement with structural motif and the g-factors evaluated from the EPR spectra are consistent with coordination sphere of distorted tetragonal symmetry for central copper(II) ions. 4-PM in complexes (1) and (2) has acted like N,O-bridging ligand forming 1D polymers as well as terminal ligand. The coordination sphere of Cu(II) ion in both complexes has been tetragonal–pyramidal. Complexes (3), (4), (5) and (6) have been found of the same type with chromophore trans – CuÓ2N2O2. Cu(II)atoms have lied in the centre of symmetry and have formed hexacoordination in the shape of a distorted octahedral. Individual copper(II) centres have been linked by bridging 4-pyridylmethanol and have formed infinite 1-D “double bridged” chains. The molecules of all complexes have been connected by OH⋯O hydrogen bonds forming supramolecular structures.

In this study, two Cu2+-doped single crystals, [Cu-0.02(H1.96L)](ClO4)(2) (1) and [Cu-0.91(H0.18L)](ClO4)(2) (2) (L =3,14- diethyl-2,6,13,17-tetraazatricyclo(16.4.0.0(7,12)) docosane), were prepared and characterized by elemental and X-ray crystal structural analyses, along with UV-visible, infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. The asymmetric units of compounds 1 and 2 contain one half of the molecular dication and one doubly disordered perchlorate anion. The macrocyclic ligand in both the Cu2+-doped compounds adopts the most stable trans-III conformation. The Cu-N bond lengths in the range 2.010 (2)-2.055 (3) angstrom are normal, but the long axial Cu1-O3 bonds of 2.836 (3) and 2.729 (3) A for 1 and 2, respectively, may be due to a combination of the Jahn-Teller effect and strong in-plane ligand field. The crystals are stabilized by hydrogen bonds involving the secondary N-H, the N atoms of the macrocycle, and the O atoms of the perchlorate groups. (C) 2019 Elsevier B.V. All rights reserved.

Various substituted 2-hydroxybenzophenones were combined with aliphatic linear triamines to form pentadentate Schiff base ligands. Twelve new iron(III) complexes with the general formula [Fe(Ln )X].mCH3 CN (n=1-10; X=N3 - , NCS- or NCSe- ; m=0-2) have been synthesized, and spectrally as well as structurally characterized. The structural analysis revealed a notable dependence of coordination polyhedra deformation as well as the spatial configuration of donor atoms on the length and symmetry of the Schiff base ligands. The magnetic properties of the compounds were investigated and the permanent high-spin state (S=5/2) for all reported compounds was established, and allowed calculation of zero-field-splitting parameters as well as coupling constants, which were further confirmed with DFT calculations. The solid-state EPR spectra were recorded at 293 K and 98 K, and in accordance with the magnetic measurements, showed a high-spin state in the measured temperature range.