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Four novel CeIII mononuclear complexes of formulas [Ce(ntfa)3(MeOH)2] (1), [Ce(ntfa)3(5,5′-Me2bipy)] (2), [Ce(ntfa)3(terpy)] (3), and [Ce(ntfa)3(bipy)2] (4), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionato, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-dipyridyl, terpy = 2,2′:6′,2″-terpyridine, and bipy = 2,2′-bipyridine, have been synthesized and structurally characterized with CeIII displaying coordination numbers of 8, 8, 9, and 10, respectively. Magnetic measurements indicate that all the complexes show a field-induced single-ion magnet behavior under a small applied dc field. The magnetic analysis shows the relevance of the different spin relaxation mechanisms in the magnetic relaxation of the CeIII compounds, with special emphasis on the local-mode process. Multiconfigurational calculations were also performed to get more information on the axiality of the compounds.

Five new eight-coordinated Nd(III) mononuclear complexes with the formulae [Nd(ntfa)3(EtOH)2] (1), [Nd(ntfa)3(phen)] (2), [Nd(ntfa)3(bipy)] (3), [Nd(ntfa)3(5,5′-Me2bipy)] (4) and [Nd(ntfa)3(4,4′-Mt2bipy)] (5), where ntfa = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate, phen = phenanthroline, bipy = 2,2′-dipyridine, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-dipyridine, and 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-dipyridine, were synthesized and structurally characterized. Magnetic measurements were carried out on complexes 2–5. Dynamic magnetic studies revealed single-molecule magnet (SMM) behavior for complexes 2, 4 and 5 with anisotropy energy barriers and preexponential factors of Ueff = 18 cm−1, τ0 = 2.2 × 10−7 s; Ueff = 31 cm−1, τ0 = 1.0 × 10−9 s and Ueff = 19 cm−1, τ0 = 8.7 × 10−8 s, respectively. The ancillary chelating bipyridyl ligands in complexes 2–5 greatly enhance the solid state luminescence emission in the visible and NIR regions through efficient energy transfer from the ligands to the central Nd3+ ion. This study highlights the bifunctionality of the Nd(III) complexes.

A series of heteroleptic copper(II) complexes of the composition [Cu(L1–5)Cl]X, where X = ClO4 and/or PF6 and [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl))-(6-methyl-(2-pyridylmethyl))]amine (L1), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl))-(3,4-dimethoxy-(2-pyridylmethyl))]amine (L2), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl)-(2-quinolymethyl)]amine (L3), [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazolyl)-(di(3,5-dimethyl-1H-pyrazol-1-yl-methyl))]amine (L4) and [bis(2-ethyl-di(3,5-dimethyl-1H-pyrazol-1-yl)-(5-methyl-3-phenyl-1H-pyrazol-1-yl-methyl)]amine (L5), were prepared and thoroughly characterized including single-crystal X-ray diffraction technique. The in vitro cytotoxicity of complexes against A2780, A2780R, HOS and MCF-7 human cancer cell lines was evaluated using the MTT test. The results revealed that complexes [Cu(L1)Cl]PF6 (1-PF6), [Cu(L2)Cl]ClO4 (2-ClO4) and [Cu(L3)Cl]PF6 (3-PF6) are the most effective, with IC50 values ranging from 1.4 to 6.3 μM, thus exceeding the cytotoxic potential of metallodrug cisplatin (IC50 values ranging from 29.9 to 82.0 μM). The complexes [Cu(L4)Cl]PF6 (4-PF6) and [Cu(L5)Cl]PF6 (5-PF6) showed only moderate cytotoxicity against A2780, with IC50 = 53.6 μM, and 33.8 μM, respectively. The cell cycle profile, time-resolved cellular uptake, interactions with small sulfur-containing biomolecules (cysteine and glutathione), intracellular ROS production, induction of apoptosis and activation of caspases 3/7 were also evaluated in the case of the selected complexes. It has been found that the best performing complexes 1 and 2 cause cell arrest in the G2/M phase and induce apoptosis via the increase in production of ROS, dominantly due to the overproduction of superoxide.

Abstract Six mixed metal complexes with 3-aminopyridine (3-ampy) as a co-ligand have been synthesized: catena-{[M(μ2-3-ampy)(H2O)4]SO4·H2O} (M=Ni (1) and Co (2)), [Co(3-ampy)4(NCS)2] (3), [Co(3-ampy)2(NCS)2] (4), [Co(3-ampy)4(N3)2] (5) and mer-[Co(3-ampy)3(N3)3] (6), (NCS−=isothiocyanate ion, N3− azide ion), and characterized by physio-chemical and spectroscopic methods as well as single crystal X-ray and powder diffraction. In the isostructural complexes 1 and 2 single μ2-3-ampy links the Ni(II) and Co(II) centers into polymeric chains. The mononuclear Co(II) and Co(III) pseudohalide complexes 3–6 reveal only terminal 3-ampy ligands. The 3-ampy ligands form supramolecular hydrogen bonded systems via their NH2-groups and non-covalent π-π ring-ring interactions via their pyridine moieties. Thermoanalytical properties were investigated for 1–3. Graphic abstract

Two penta-coordinate complexes of the general formula [Co(Ln)(NCS)]ClO4, where L1 = {bis[(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]-[(3,4-dimethoxypyridin-2-yl)methyl]}amine and L2 = {bis[(3,5-dimethyl-1H-pyrazol-1-yl)ethyl]-[(4-methoxy-3,5-dimethylpyridin-2-yl)methyl]}amine, have been synthesized and thoroughly characterized. Each of the cobalt(ii) atoms is penta-coordinated in the {CoN5} donor set with a distorted square-pyramidal geometry in [Co(L1)(NCS)]ClO4·MeOH (1), while the vicinity of the central atom can be described as a distorted trigonal-bipyramidal geometry in [Co(L2)(NCS)]ClO4 (2) as revealed using the SHAPE analysis. Differences in interatomic parameters among the cobalt(ii) and donor atoms in 1 and 2 have definite impact on the magnetic features of both compounds. The complexes show an easy-axis magnetic anisotropy (D = -38.5 cm-1 for 1 and D = -8.5 for 2), and both complexes reveal a large rhombicity with E/D = 0.21 for 1 and E/D = 0.29 for 2. The ZFS parameters (g, D and E) were also calculated using CASSCF/NEVPT2 methods and they are in good agreement with those determined from experimental data. A frequency dependent out-of-phase susceptibility has been observed in external magnetic field (Bdc = 0.1 T) revealing the following parameters of slow relaxation of magnetization for 1: energy of the spin reversal barrier, Ueff = 16.0 cm-1 (Ueff/kB = 23.0 K) and the relaxation time, τ0 = 1.28 × 10-6 s. In the case of complex 2, no maxima of frequency dependent out-of-phase susceptibility have been observed and thus, the value of Ueff = 17 cm-1 has been estimated using the expression Ueff = |D| × (S2 - 1/4). It has been demonstrated that the degree of substitution and the type of substituents on the pyridyl moieties of the tripodal ligands (L1 and L2) used in these penta-coordinate cobalt(ii) complexes have significant impact on structural and magnetic features.

Two cationic [Cu

Six pseudohalide zinc(II) containing a variety of N-donor auxiliary amines were structurally characterized. These include two mononuclear trigonal bipyramidal [Zn(NTB)(N3)]ClO4·½H2O (3) and [Zn(TPA)(NCS)]ClO4 (4), two distorted octahedral [Zn(1,8-damnph)2(dca)2] (5) and [Zn(8-amq)2(dca)2] (6a) as well as two 1D polymeric chains catena-[Zn(isq)2(μ1,5-dca)2] (7) and catena-[Zn(N,N-Me2en)2(μ1,5-dca)]dca (8), where NTB = tris(2-benzimidazolylmethyl)amine, TPA = tris(2-pyridylmethyl)amine, 1,8-damnph = 1,8-diaminonaphthalene, 8-amq = 8-amino-quinoline, isq = isoquinoline (isq) and N,N-Me2en = N,N-dimethylethylenediamine. In general, with the exception of 6 and 8, the complexes exhibited luminescence emission in MeOH associated with red shift of the emission maxima, and the strongest visible fluorescence peak was detected at 421 nm (λex = 330 nm) in the case of Complex 5.

Two coordination polymers of mono-dimensional doubly bridged-azido-cobalt(II) complexes catena-[Co(2,6-lutidine-N-oxide)(μ1,1-N3)2] (1) and catena-{[Co(μ1,1-N3)2(H2O)2](3-picoline-N-oxide)2} (2), where 2,6-lutidine-N-oxide = 2,6-dimethylpyridine-N-oxide and 3-picoline-N-oxide = 3-methylpyridine-N-oxide, were synthesized, and structurally characterized by single crystal X-ray crystallography. The Co(II) cations in complexes 1 and 2 are penta- and hexa-coordinate, respectively with four μ1,1-bridging azido groups and a terminal 2,6-lutidine-N-oxide molecule in 1 or two trans aqua molecules in 2. Magnetic relaxations in the zero field are consistent with single chain magnetic behavior (SCM) and the ac susceptibility measurements revealed that the weak ferromagnetic exchanges in the two complexes are associated with slow relaxation of magnetization. Complex 2 exhibits metamagnetic transition with an antiferromagnetic phase transition at 12 K at the applied field of 200 Oe.

Five new metal(II) dicyanamido (dca) complexes with 3-aminopyridine (py-NH2) have been synthesized, catena-[M(μ1,5-dca)2(py-NH2)2] {M = Mn (1), Cu (2), Co (3), Zn (4) and Cd (5)}, and characterized by elemental analysis, IR, UV–Vis spectroscopy, single crystal X-ray and powder diffraction, respectively. The isostructural polymeric 1D complexes feature double µ1,5-bridging dicyanamide ligands and two terminal 3-aminopyridine ligands located in a trans-conformation around the distorted M(II) octahedra, which add extra stability through their involvements in the formation of 3D supramolecular hydrogen bonded systems and the constitution of non-covalent π–π ring-ring interactions along the chain direction. The magnetic properties of complexes 1–3 were studied at variable temperature over the range 2–300 K. Luminescence enhancements upon complexation of dca ligands was observed in 4 and 5.

A dimeric [Cu(μ-4-HOMP)(4-HOMP)(NCS)2]2 (1) and three discrete monomeric complexes [Ni(3-HOMP)2(NCS)2(H2O)2] (2), [Co(3-HOMP)3(N3)3]·H2O (3) and [Zn(4-HOMP)2(NCS)2] (4), (3-HOMP = 3-hydroxymethylpyridine, 4-HOMP = 4-hydroxymethylpyridine) have been isolated and structurally characterized by IR, UV–Vis spectroscopy, XRPD, single crystal X-ray crystallography and Hirshfeld surface analysis as well as thermogravimetric analyses for complexes 1, 2 and 4. In dimeric complex 1 each penta-coordinated Cu2+ center is bridged through N,O-4-HOMP ligands, whereas metal ions in 2 and 3 are located in distorted octahedral geometry with mer-configuration in the azido complex 3. Distorted tetrahedral geometry is observed around Zn2+ in complex 4. The variable temperature magnetic susceptibility measurements of 1 showed very weak antiferromagnetic interaction.

The complexes [Cu(TPA)Cl]ClO4·½H2O (1-ClO4), [Cu(6-MeTPA)Cl]ClO4/PF6 (2-ClO4/2-PF6), [Cu(6-Me2TPA)Cl]PF6 (3-PF6), [Cu(BPQA)Cl]ClO4/PF6 (4-ClO4/4-PF6), [Cu(BPQA)Cl]ClO4/PF6 (4-ClO4/4-PF6), [Cu(BQPA)Cl]ClO4/PF6 (5-ClO4/PF6), [Cu(L1)Cl]ClO4/PF6 (6-ClO4/6-PF6), [Cu(L2)Cl]ClO4 (7-ClO4) and [Cu(L3)Cl]ClO4 (8-ClO4) have been synthesized and structurally characterized by spectroscopic techniques and single X-ray crystallography. The in vitro cytotoxicity of the prepared Cu(II) complexes was evaluated against A2780 (ovarian), A2780R (cisplatin-resistant variant) and MCF7 (breast cancer) human cancer cell lines. Overall, the complexes revealed significant-to-moderate cytotoxicity, with the best results obtained for the complexes [Cu(BQPA)Cl]ClO4 (5-ClO4) and [Cu(BQPA)Cl]PF6 (5-PF6), showing IC50 values within the range of 4.7–10.8 μM. The ability of the most cytotoxic complexes to cleave DNA under different conditions and the mechanisms underlying this activity were assessed by means of agarose gel electrophoresis.

The synthesis and structural characterization of six dicyanamido-cadmium(II) complexes are reported: catena-[Cd(μ1,3-dca)(μ1,5-dca)(3-ampy)] (1), catena-[Cd3(μ1,3,5-dca)2(μ1,5-dca)4(pyNO)2(H2O)2] (2), catena-{Cd(H2O)2(μ1,5-dca)2](2,6-lut-NO)} (3), catena-[Cd(Me2en)(μ1,5-dca)2] (4), catena-[Cd(Me4en)(μ1,5-dca)2] (5), and [Cd(1,8-damnp)2(dca)2] (6), where dca = dicyanamide anion, 3-ampy = 3-aminopyridine, pyNO = pyridine-N-oxide, 2,6-lut-NO = 2,6-lutidine-N-oxide, Me2en = N,N-dimethyl-ethylenediamine, Me4en = N,N,N′,N′-tetramethyl-ethylenediamine, and 1,8-damnp = 1,8-diaminonaphthaline. The coordination polymers have different dimensionalities: 1 and 5 form 3D networks structures, 3 and 4 form polymeric 1D chains and 1DD double chains, respectively. Ribbons of three fused polymeric chains are observed in 2. In 6, the mononuclear complex units form a hydrogen-bonded supramolecular 3D network. In the coordination polymer compounds, the dca linkers display three bonding modes: the most common μ1,5-dca and the least popular μ1,3- and μ1,3,5-dca bonding. The luminescence emission and thermal properties of the complexes were investigated.

Three cobalt(II) isothiocyanato complexes with 4-methoxypyridine (4-MOP) as a co-ligand have been synthesized: catena-[Co(4-MOP)2(μ1,3-NCS)2] (1), trans-[Co(4-MOP)4(NCS)2] (2), and [Co(4-MOP)2(NCS)2] (3) and structurally characterized by IR, UV–Vis spectroscopy and single crystal X-ray diffraction. The complexes 2 and 3 are discrete monomeric species with octahedral and tetrahedral geometries, respectively whereas the catena-[Co(4-MOP)2(μ1,3-NCS)2] (1) is featuring a polymeric 1D system with doubly bridging NCS− groups through the terminals N- and S-donor atoms in a trans octahedral geometry. The thermoanalytical behavior of 1–3 is reported. Magnetic susceptibility of the bridged-isothiocyanato coordination polymer 1 was studied down to a temperature of 2 K and at various magnetic dc and ac fields. These measurements indicate a metamagnetic transition in 1.

Four different coordination compounds have been synthesized and structurally characterized in the reaction of aqueous solution of Mn(NO3)2 with pyridine-N-oxide co-ligands in the presence of KNCS, namely: [Mn(2-methylpyridine-N-oxide)(NCS)2]n (1); [Mn(3-methylpyridine-N-oxide)2(NCS)2]n (2), [Mn(4-methylpyridine-N-oxide)2(NCS)2(H2O)2] (3) and [Mn(4-cyanopyridine-N-oxide)2(NCS)2(H2O)]2 (4). Single crystal X-ray crystallography revealed the polymeric nature of the complexes as 2-D and 1-D for 1 and 2, respectively, with doubly μ(N,S) isothiocyanato bridging and μ(O,O) bridging methylpyridine-N-oxide ligands. The metal centers in the dinuclear complex 4 are linked by doubly μ(N,S) isothiocyanato bridges, whereas only terminal ligands are observed in the mononuclear complex 3. The magnetic properties of the complexes 1, 2 and 4 were investigated over the temperature range 2–300 K.

A series of pentacoordinate Co(II) complexes of the composition [Co(bpdmpz)Cl]ClO4 (1), [Co(bpdmpz)Cl]PF6 (2), [Co(bdmpzp)Cl]ClO4·H2O (3), [Co(bdmpzp)Cl]PF6 (4), [Co(tdmpza)Cl]ClO4 (5) and [Co(tdmpza)Cl]PF6 (6) (bpdmpz = bis[(2-pyridylmethyl)-(di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine, bdmpzp = bis[(di(3,5-dimethyl-1H-pyrazolyl)methyl))-(2-pyridylmethyl)]amine and tdmpza = tris[di(3,5-dimethyl-1H-pyrazolyl)methyl)]amine) was prepared and thoroughly characterized. Single-crystal X-ray analyses of complexes 1–5 revealed that they possess very close molecular structures with a distorted trigonal bipyramidal geometry. The static DC magnetic experiments revealed the ZFS parameters pointing out small magnetic anisotropy (with the |D| values lying in a relative narrow range of 4.4–5.7 cm−1) and rhombicity (with the E/D parameters in the range of 0–0.26). The dynamic magnetic data revealed that AC susceptibility is temperature and frequency-dependent for 1, 2 and 3, and thus, these compounds belong to a group of field-induced pentacoordinate Co(II) single-molecule magnets (SMMs). The evaluation of magnetic data was also supported by the CASSCF/NEVPT2 calculations.

Ten mononuclear rare earth complexes of formula [La(btfa)3(H2O)2] (1), [La(btfa)3(4,4′-Mt2bipy)] (2), [La(btfa)3(4,4′-Me2bipy)2] (3), [La(btfa)3(5,5′-Me2bipy)2] (4), [La(btfa)3(terpy)] (5), [La(btfa)3(phen)(EtOH)] (6), [La(btfa)3(4,4′-Me2bipy)(EtOH)] (7), [La(btfa)3(2-benzpy)(MeOH)] (8), [Tb(btfa)3(4,4′-Me2bipy)] (9) and (Hpy)[Eu(btfa)4] (10), where btfa = 4,4,4-trifuoro-1-phenylbutane-1,3-dionato anion, 4,4′-Mt2bipy = 4,4′-dimethoxy-2,2′-bipyridine, 4,4′-Me2bipy = 4,4′-dimethyl-2,2′-bipyridine, 5,5′-Me2bipy = 5,5′-dimethyl-2,2′-bipyridine, terpy = 2,2′:6′,2′-terpyridine, phen = 1,10-phenathroline, 2-benzpy = 2-(2-pyridyl)benzimidazole, Hpy = pyridiniumH+ cation) have been synthesized and structurally characterized. The complexes display coordination numbers (CN) eight for 1, 2, 9, 10, nine for 5, 6, 7, 8 and ten for 3 and 4. The solid-state luminescence spectra of Tb-9 and Eu-10 complexes showed the same characteristic bands predicted from the Tb(III) and Eu(III) ions. The Overall Quantum Yield measured (ϕTOT) at the excitation wavelength of 371 nm for both compounds yielded 1.04% for 9 and up to 34.56% for 10.

Three metal(II) dicyanamide (dca) complexes have been synthesized in presence of 2,6-lutidine-N-oxide (2,6-lut-NO): catena-{[M(μ1,5-dca)2(H2O)2](2,6-lut-NO)} (M = Mn(II) (1) , Co(II) (2), Ni(II) (3)), and characterized by IR, UV–Vis spectroscopy, single crystal and powder X-ray diffraction. The isostructural polymeric 1-D complexes feature double µ1,5-bridging dicyanamide ligands and terminal aqua ligands in trans-conformation around the distorted M(II) octahedra, whereas the 2,6-lutNO molecules are not ligated to the metal centers. The magnetic and thermal properties of the title complexes are reported.

Five new metal(II) dicyanamide (dca) complexes with 4-hydroxymethylpyridine (4-OMP) and 4-methoxypyridine (4-MOP) have been synthesized, [Co(dca)2(4-OMP)2]n (1), [Cu(dca)2(4-OMP)2]n (2), [Cu(dca)2(4-MOP)2]n (3), [Cd(dca)2(4-MOP)2]n (4), [Zn(dca)2(4-MOP)2]n (5) and characterized by IR, UV–Vis spectroscopy and single crystal X-ray diffraction. The isostructural polymeric 1-D complexes feature double µ1,5-bridging dicyanamide ligands and terminal 4-OMP or 4-MOP ligands in trans-conformation around the distorted M(II) octahedra. The magnetic properties of complexes 1 and 2 are reported.

Four 1D coordination polymers catena -[Cu(4-HOCH 2 py)(μ 1,1 -N 3 )(μ 1,3 -N 3 )] ( 1 ), catena -[Cu(3-MeOpy) 2 (µ 1,1 -N 3 ) 2 ] ( 2 ), catena -[Cu(2-Br-4-Mepy)(µ 1,1 -N 3 ) 2 ] ( 3 ) and catena -[Cu(μ O,O -2-Cl-6-Menic)(μ 1,1 -N 3 )(MeOH)] ( 4 ) where 4-HOCH 2 py, 3-MeOpy, 2-Br-4-Mepy and 2-Cl-6-Menic represent 4-pyridylmethanol, 3-methoxypyridine, 2-bromo-4-methylpyridine and 2-chloro-6-methyl nicotinate anion, respectively have been synthesized, and structurally and magnetically characterized. Variable temperature magnetic susceptibility measurements over the temperature range 4.5–300 K revealed weak to moderate ferromagnetic coupling on going from complexes 1 ( J = 10.1 cm −1 ) and 3 ( J = 16 cm −1 ) to 4 ( J = 51.1) cm −1 . On the other hand, complex 2 displayed weak antiferromagnetic coupling ( J = −3.82 cm −1 ). The magnetic properties of the complexes are discussed in relation to the structural parameters of the bridging ligands.

Three different coordination polymeric compounds have been synthesized and structurally characterized in the reaction of aqueous solution of Mn(NO3)2·4H2O with methylpyridine-N-oxide co-ligands (Mepy-N-oxide) in the presence of NaN3 depending on the position of the methyl group in Mepy-N-oxide namely: [Mn(μ(O,O)-2-Mepy-N-oxide)(μ1,3-N3)2]n (1), catena-{[Mn(μ1,1-N3)2(H2O)2](3-Mepy-N-oxide)2} (2) and [Mn3(μ1,1-N3)2(μ1,3-N3)4(μ(O,O)-4-Mepy-N-oxide)2(H2O)2]n (3). Single crystal X-ray crystallography revealed the polymeric nature of the complexes as 2D, 1D and 3D networks, respectively with a doubly end-to-end (EE) azide bridging and μ(O,O) bridging 2-Mepy-N-oxide in 1, and a doubly end-on (EO) azide bridging in 2. In complex 3 within the trinuclear subunit the three Mn(II) atoms are bridged via EO azido groups and μ(O,O) bridging 4-Mepy-N-oxide molecules and the trinuclear subunits are connected further by EE azido bridges to generate the 3D network structure. The magnetic properties of the three complexes were investigated over the temperature range 2–300 K. Complex 2, as far as we know, is the first Mn(II) uniform 1D compound with double EO azido bridges which shows antiferromagnetic coupling. The fit of the magnetic data by using the appropriate equation derived from the Hamiltonian H = −∑JSi·Si+1 gives the best fit parameters J = −3.55(1) cm−1, g = 2.044(1).

Five coordination polymers catena-[(3-Hampy)2[Zn7(N3)16(3-ampy)4]·3H2O] (1), catena-[Zn2(μ2-4-HO-py)(μ1,1-N3)4]·H2O (2), catena-[Zn2(μ2-4-amtz)(μ1,1-N3)4] (3), catena-[Zn(5-Et-2-Me-py)(μ1,1-N3)2] (4) and catena-[Zn(μ2-2-O-py-N-oxide)(μ1,1-N3)] (5), where 3-ampy = 3-aminopyridine, 4-HOpy = 4-hydroxypyridine, 4-amtz = 4-amino-4H-1,2,4-triazole, 5-Et-2-Mepy = 5-ethyl-2-methylpyridine and 2-HO-py-N-oxide = 2-hydroxypyridine-N-oxide were synthesized and structurally characterized by single crystal X-ray crystallography. The complexes display different dimensionality depending on the nature of the coligand. The anionic polymer in complex 1 consists of 1D system of defective dicubanes with two different azido-bridging μ1,1-N3 and μ1,1,1-N3 modes. Complexes 2 and 3 are isostructural and both exhibit 2D networks with μ(O,O)-pyridinone bridging molecule in 2 or μ(N,N′)-bridging 4-amtz in 3, and μ1,1,-azide bridging. Complex 4 reveals a zigzag chains of 1D polyhedral through a doubly bridged μ1,1-N3 bonding mode, whereas in complex 5 a 1D polymeric chain is generated via singly bridged μ1,1-N3 bonding and hydrogen bonding results in the formation of supramolecular 2D system. The emission spectral properties of the parent free ligands and their corresponding Zn(II) complexes were investigated where enhancement luminescence emissions with strong red shifts were observed in complexes 2, 4 and 5.

Two dinuclear complexes namely [(UO2)2(L1)2(DMSO)2] (1) and [(UO2)2(L2)2(DMSO)2] (2) of two Schiff base ligands 2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-2-hydroxymethyl propane-1,3-diol (HL1) and 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-2-hydroxymethyl-propane-1,3-diol (HL2) obtained by condensation of the aldehydes 2-hydroxy-3-methoxy-benzaldehyde and 3, 5-dichloro salicylaldehyde with tris(hydroxymethyl)aminomethane ammine, have been synthesized. On the other hand, when the two aldehydes were treated with uranyl nitrate two mononuclear complexes, [(UO2)(L3)2(DMSO)2] (3) and [(UO2)(L4)2(DMSO)2] (4), are obtained. The complexes are then heated at 800 °C in open atmosphere to obtain the U3O8 nanomaterials as the final product. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to characterize the so obtained the U3O8 nanoparticles. Studies shows the synthesized U3O8 nanoparticles obtained from different complexes were different as far as morphology and size are concerned. All four different U3O8 nanoparticles explored as oxidising catalyst to oxidize alcohols where morphology of the nanoparticles controls the catalytic efficiency.

Reactions of a methanolic solution containing M(NO3)2·nH2O and bis(2-(H-pyrazol-1-yl)ethyl)amine (bepza) with NH4NCS afforded two series of complexes: the mononuclear dithiocyanato [M(bepza)(NCS)2] (1: M = Mn2+, 2: M = Zn2+, 3: M = Cu2+, 5: M = Ni2+) and the dinuclear bridged-thiocyano [M2(bepza)2(μ1,3-NCS)2(NCS)2] (6: M = Cd2+, 7: M = Co2+). The compounds which proved to be non-electrolytes were characterized by IR and UV–Vis spectroscopy and the molecular structures of the compounds 1–3, 6 and 7 were determined by single-crystal X-ray crystallography. In the former series, the five-coordinate distorted square pyramidal or trigonal bipyramidal geometry was achieved by the three N-donors of the ligand bepza and two N atoms of the terminal thiocyanato ligands, whereas in the dinuclear series, distorted octahedral geometry around each metal ion was achieved via the three N-donors of bepza, one N atom of a terminal thiocyanato ligand and a doubly bridged μ1,3-NCS.

La0.7Sr0.3(Fe0.2Co0.8)O3 and La0.7Sr0.3MnO3 −based cathode catalysts are synthesized by the sol-gel method. These perovskite cathode catalysts are tested in half cell configuration and compared to MnO2 as reference material in alkaline direct ethanol fuel cells (ADEFCs). The best performing cathode is tested in single cell setup using a standard carbon supported Pt0.4Ru0.2 based anode. A backside Luggin capillary is used in order to register the anode potential during all measurements. Characteristic processes of the electrodes are investigated using electrochemical impedance spectroscopy. Physical characterizations of the perovskite based cathode catalysts are performed with a scanning electron microscope (SEM) and by X-ray diffraction showing phase pure materials. In half cell setup, La0.7Sr0.3MnO3 shows the highest tolerance toward ethanol with a performance of 614 mA cm−2 at 0.65 V vs. RHE in 6 M KOH and 1 M EtOH at RT. This catalyst outperforms the state-of-the-art precious metal-free MnO2 catalyst in presence of ethanol. In fuel cell setup, the peak power density is 27.6 mW cm−2 at a cell voltage of 0.345 V and a cathode potential of 0.873 V vs. RHE.

A set of tetra- and dinuclear copper(II) complexes, [Cu4(L1)(μ-O)(OAc)4] (1), [Cu2(L2)2](ClO4)2 (2), [Cu2(L2)2(OAc)2] (3), [Cu2(L2)2(Br)2] (4) and [Cu2(L2)2(Cl)2] (5), were synthesized from two Mannich-base ligands HL1 and HL2, where HL1 = 2,6-bis[bis(2-methoxyethyl)aminomethyl]-4-methylphenol and HL2 = 2-[bis(2-methoxyethyl)aminomethyl]-4-methylphenol. The catalytic efficiency of the complexes for catecholase activity was systematically evaluated by spectrophotometry using 3,5-di-tert-butylcatechol (3,5-DTBC) and tetrachlorocatechol (TCC) in pure dry acetonitrile (MeCN) and water–MeCN solvent mixtures (10%, 25%, 40% and 50% water). In spite of remarkable rate enhancements by the tetranuclear species in MeCN (kcat = 0.0218 s−1), complex 1 follows a reverse trend in the solvent dependent kinetic study compared to complexes 2–5 with a minimum at 25% water (kcat = 0.0118 s−1) under similar experimental conditions. Theoretical modeling involving the reactions of complexes 1, 3 and 5 provides the counterintuitive rationalization of the apparently dramatic behaviour of these novel catechol models on addition of water to the MeCN solution. More importantly, it vindicates the combination of the contradictory parameters like alcoholysis and hydrolysis as the governing factors for kcat extrema in catalytic pathways. Thus, the reactivity and mechanism of Mannich-base metallocatalysts across water-induced oxidation of catechols is predictable through their nuclearity.

Three croconato-bridged Cu(II) complexes were synthesized and structurally characterized including dinuclear [Cu2(Et4dien)2(μ1,2,3,4-C5O5)](ClO4)2·3H2O (1) and [Cu2(pmap)2(μ1,2,3,4-C5O5)](ClO4)2·2H2O (2) and the 1D coordination polymer {[Cu(dmpzp)(μ1,2,3,4-C5O5)]·H2O}n (3), where Et4dien = N,N′,N′′,N′′-tetraethylethylenetriamine, pmap = bis(2-(2-pyridyl)ethyl)-(2-pyridylmethyl)amine and dmpzp = 1-(2-methylpyridyl)-3,5-dimethyl-1-H-pyrazole. The synthesized complexes were further characterized by a single crystal X-ray analysis which revealed the bis-bidentate chelating nature of the μ1,2,3,4-croconato ligand with the intra-dimer Cu⋯Cu bond distances ranging from 6.79 to 7.69 A across the bridged croconate. The magnetic susceptibility measurements at varying temperatures (1.9–300 K) showed that the complexes exhibit a weak antiferromagnetic (AF) coupling with J values = −2.67 cm−1 for 1 and 2, and −4.05 cm−1 for 3. The weak AF coupling was also predicted based on the DFT calculations. The magnetic properties of the complexes are discussed in light of their structures and compared with the previously reported croconato-bridged Cu(II) complexes.

Five-coordinate Cu(II) complexes, [Cu(Ln)X]ClO4/PF6, where Ln = piperazine ligands bearing two pyridyl arms and X = ClO4− for Ln = L1 (1-ClO4), L2 (2-ClO4), L3 (3-ClO4), and L6 (6-ClO4) as well as [Cu(Ln)Cl]PF6 for Ln = L1 (1-Cl), L4 (4-Cl), and L5 (5-Cl) have been synthesized and characterized by spectroscopic techniques. The molecular structures of the last two complexes were determined by X-ray crystallography. In aqueous acetonitrile solutions, molar conductivity measurements and UV-VIS spectrophotometric titrations of the complexes revealed the hydrolysis of the complexes to [Cu(Ln)(H2O)]2+ species. The biological activity of the Cu(II) complexes with respect to DNA cleavage and cytotoxicity was investigated. At micromolar concentration within 2 h and pH 7.4, DNA cleavage rate decreased in the order: 1-Cl ≈ 1-ClO4 &gt, 3-ClO4 ≥ 2-ClO4 with cleavage enhancements of up to 23 million. Complexes 4-Cl, 5-Cl, and 6-ClO4 were inactive. In order to elucidate the cleavage mechanism, the cleavage of bis(4-nitrophenyl)phosphate (BNPP) and reactive oxygen species (ROS) quenching studies were conducted. The mechanistic pathway of DNA cleavage depends on the ligand’s skeleton: while an oxidative pathway was preferable for 1-Cl/1-ClO4, DNA cleavage by 2-ClO4 and 3-ClO4 predominantly proceeds via a hydrolytic mechanism. Complexes 1-ClO4, 3-ClO4, and 5-Cl were found to be cytotoxic against A2780 cells (IC50 30–40 µM). In fibroblasts, the IC50 value was much higher for 3-ClO4 with no toxic effect.

The synthesis and structural characterization of two new complexes catena -[Ni(3-O-py)(3-HO-py) 2 (μ 1,3 -N 3 )(H 2 O)] ( 1 ) and catena -[Zn(μ-3-O-py)(μ 1,1 -N 3 )] ( 2 ), where 3-HO-py = 3-hydroxypyridine, are reported. The complexes were characterized by the elemental microanalyses, IR, and X-ray crystallography and by UV–Vis spectroscopy for complex 1 . Single crystal X-ray crystallography revealed the polymeric nature of the complexes: 1 as 1D with a single EE azide bridging, and 2 as 2D with μ(O,O′,N) bridging of the deprotonated 3-O-py anions and di-EO azide groups, respectively. In 1 the neutral and deprotonated 3-hydroxypyridine molecules act only as N-terminal ligands. The emission spectral properties of the Zn(II) complex were investigated.

The reaction of a methanolic solution containing MIICl2 (M = Co or Cu) with bis(3,5-dimethyl-1H-pyrazol-1-yl-1-ethyl)(2-pyridylmethyl)amine (bedmpzp) in the presence of NH4PF6 afforded the dinuclear doubly bridged-dichlorido complex [Co2(bedmpzp)2(μ-Cl)2](PF6)2 (1) and the mononuclear [Cu(bedmpzp)Cl]PF6 (2) one. The complexes were structurally and magnetically characterized. The weak ferromagnetic exchange and the axial type of magnetic anisotropy found in 1 is associated with slow relaxation of magnetization as revealed by AC susceptibility measurements. This finding puts 1 into a class of polynuclear single-molecule magnets based on 3d metals. X-ray structure of 2 revealed mononuclear nature of the complex, forming supramolecular dimers in the solid state. The non-covalent interactions of the Cu⋅⋅⋅Cl type present in its crystal structure induced a weak antiferromagnetic exchange. The results of magnetic analysis were also supported by DFT and CASSCF/NEVPT2 calculations. The in vitro cytotoxicity of the complexes against MCF7 and HeLa human cancer cell lines were also tested. The best cytotoxicity was achieved for complex 2 on HeLa, with IC50 = 2.5(0.9) μM.

The synthesis and structural characterization of the complexes catena-[Cd(2,6-lutidine-N-oxide)(μ1,1-N3)(μ1,1,1-N3)] (1), catena-[Cd(μ2-2,6-lutidine-N-oxide)(μ1,3-NCS)2] (2), catena-[Zn(2,6-lutidine-N-oxide)(μ1,1-N3)2] (3) and [Zn(2,6-lutidine-N-oxide)2(NCS)2] (4) where 2,6-lutidine = 2,6-dimethylpyridine-N-oxide, are reported. Single crystal X-ray crystallography revealed the polymeric nature of complexes 1, 2, and 3 as a 1D double chains “ladder of defective cubane”, 2D with doubly μ(O,O) bridging of 2,6-lutidine-N-oxide and 1D, respective, and the monomeric nature of 4. The emission spectral properties of the complexes were investigated and fluorescence enhancement was observed for complexes 2–4.

The synthesis and structural characterization of six new d10 Cd(II) and Zn(II) thiocyanato complexes with pyridine-N-oxide compounds: the polymeric catena-[Cd(μ2-2-picoline-N-oxide)(μN,S-NCS)2] (1), catena-[Cd(μ2-3-picoline-N-oxide)(μN,S-NCS)2] (2), catena-[Cd(4-nitropyridine-N-oxide)2(μN,S-NCS)2] (3), the dinuclear [Cd(4-cyanopyridine-N-oxide)2(μN,S-NCS)(NCS)(H2O)]2 (4) and the mononuclear complexes [Zn(2-picoline-N-oxide)2(NCS)2(H2O)] (5) and [Zn(4-cyanopyridine-N-oxide)2(NCS)2(H2O)] (6) are reported. Single crystal X-ray crystallography revealed the 2D polymeric nature in complexes 1 and 2, the 1D chain in 3 and the dimeric structure in complex 4 with the doubly-bridged Cd(μN,S-NCS)2Cd moiety. Five-coordinate monomeric Zn(II) complexes were obtained in 5 and 6, where the thiocyanto ligands are acting as monodentate N-bonded. The emission spectral properties of the six complexes were investigated. Very strong enhancing fluorescence intensity was observed in complex 3.

Two categories of polynuclear Cu(II) complexes bridged by multicarboxylate compounds 2,5-pyridine dicarboxylic acid (H2Py2,5-dc), 2,4-pyridine dicarboxylic acid (H2Py2,4-dc), 2,3-pyrazine dicarboxylic acid (H2Pyaz2,3-dc) and terephthalic acid (H2tp) have been isolated with the tripod N4-donor ligands tris(2-pyridylmethyl)amine (TPA) and tris(2-isopropyl-2-aminoethyl)amine (iptren). The trinuclear bridged-carboxylato species were obtained with TPA: [(TPA)Cu-(μ2-Py2,4-dc)2Cu(H2O)2-Cu(TPA)](ClO4)2·2H2O (1), [Cu(TPA)-Cu(μ2-Py2,5dc)2-Cu(TPA)](ClO4)2 (2) and [(TPA)Cu-(μ2-Pyaz2,3-dc)2Cu(ClO4)2-Cu(TPA)][Cu(TPA)(H2O)]2(ClO4)4·4H2O (3), and the dinuclear species [Cu2(iptren)2(tp)](ClO4)2 (4) and [Cu2(iptren)2(Pyaz2,5-dc)](ClO4)2·H2O (5) with iptren. The synthesized complexes were characterized by elemental microanalyses, conductivity measurements, IR and UV–Vis spectroscopic techniques as well as by single crystal X-ray crystallography. The nature of polycarboxylate compounds used and the coligands skeletal structure play crucial role in adopting certain carboxylate-bonding mode and the nuclearity of the coordination product.

The synthesis and structural characterization of two new polymeric zinc(II) azido complexes with pyridine- N -oxide derivative co-ligands, namely catena- [Zn(4-methylpyridine- N -oxide)(μ 1,1 –N 3 ) 2 ] ( 1 ) and catena- {[Zn 2 (μ 2 -isonicotinato- N -oxide) 2 (μ 1,1 –N 3 ) 2 (H 2 O) 3 ](H 2 O)} ( 2 ) are reported. Single crystal structure determination revealed the penta-coordinated geometry of the Zn(II) centers in the polymeric chains of 1 with di-EO azido bridging mode, whereas five and six coordination modes around Zn(II) centers are observed in complex 2 , and the 1D system is formed via alternating single EO-azide and μ(O,O′)-bridging carboxylate group of the isonicotinato- N -oxide molecules. The solid state luminescence properties of 1 were examined.

Lead Zirconate Titanate (PZT) ceramics Pb 1−1.5 x Bi x V Pb ′′ 0.5 x Zr 0.90 Ti 0.10 O 3 containing Bismuth ( x = 0.005–0.12) were structurally and dielectrically characterized. Results are compared to Lanthanum modified Pb 1−1.5 x La x V Pb ′′ 0.5 x Zr 0.90 Ti 0.10 O 3 , ( x = 0.01–0.08) ceramics. For Bi a solubility limit is observed at x = 0.04. The Lanthanum-doped series proved to be single phase in the investigated range. Lanthanum doping leads to a continuous reduction of cell volume causing a change from rhombohedral to orthorhombic symmetry at x = 0.03 accompanied by switching from ferroelectric to antiferroelectric behaviour. Such a change was not observed with Bismuth. This might be due to the fact that a critical cell volume necessary for structural transition could not be achieved within the solubility range. For Lanthanum doped PZT with x = 0.03 orthorhombic structure was determined already at room temperature, but with ferroelectric polarization curve, which switched to antiferroelectric polarization at 120 °C. This raises new questions on the appearance and stability of antiferroelectric ordering.