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A synthetically controllable two-step spin transition was observed in iron(ii) spin crossover nanoparticles of the dehydrated one-dimensional coordination polymer [Fe(NH2trz)3]Br2 (NH2trz = 4-amino-1,2,4-triazole) using the reverse micellar method.

Aminated silica hybrid, spin-crossover (SCO) nanoparticles (AmNPs) coupled with (S)-naproxen (NAP) are good candidates for drug nanocarriers.

Two three-dimensional (3-D) polycyanidometallate-based luminescent thermometers with the general formula {Ln4Co4(CN)24(4-benpyo)17(H2O)·7H2O}nLn = (Dy(III)(1), Eu(III)(2)), based on the red-emissive diamagnetic linker [Co(CN)6]3-and the bulky pyridine derivative that possesses the N-oxide moiety, 4-benzyloxy-pyridine N-oxide (benpyo), were prepared for the first time. The structure of compound 1 has been determined by single-crystal X-ray crystallography while the purity and structure of 2 have been confirmed by CHN, Fourier transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (PXRD) analysis. Magnetic AC susceptibility measurements at zero field show no single-molecule magnet (SMM) behavior indicating fast relaxation operating in 1. Upon application of an optimal field of 2 kOe, the SMM character of compound 1 is revealed while the τ can be reproduced solely considering the Raman process τ-1= CTnwith C = 7.0901(3) s-1K-nand n = 3.58(1), indicating that a high density of low-lying states and optical as well as acoustic phonons play a major role in the relaxation mechanism. Micron-sized superconducting quantum interference device (μ-SQUID) loops show a very narrow opening in agreement with the AC susceptibility studies and complete active space self-consistent field (CASSCF) calculations. The interaction operating between the Dy(III) ions was quantified from CASSCF calculations. Good agreement is found by fitting the experimental DC χMΤ(Τ) and M(H), employing the Lines model, with JLines=-0.087 cm-1(-0.125 K). The excitation spectra of compound 2 are used for temperature sensing in the 25-325 nm range with a maximum relative thermal sensitivity, Sr= 0.6% K-1at 325 K, whereas compound 1 operates as a luminescent thermometer based on its emission features in the temperature range of 16-350 K with Sr≈ 2.3% K-1at 240 K published

A reverse micelle method was used for the synthesis of water-soluble silica hybrid, spin-crossover (SCO) nanoparticles (NPs). MRI experiments provided temperature dependent T2 values, indicating their potential use as smart MRI agents, while lyophilization of NP dispersions in water yielded powders with a preserved but modified thermal hysteretic magnetic profile.

Spin Crossover (SCO) particles at the nanometric scale provide an alternative point of view and a new perspective concerning the development of a new generation of spintronic, electronic, photonic and mechanical devices. The coexistence of the SCO phenomenon with the accompanying hysteresis loop enhances the functionality of future devices for storing and processing information. Despite all promising facts, the SCO phenomena are greatly affected by cooperativity issues resulting in a direct relation between the decrease of the size of nanopatricle and the overall decrease of cooperativity towards more gradual spin transitions. This minireview aims to summarise the synthetic techniques for the synthesis of 2-D FeII SCO particles at the nanometric scale, an underexplored area of research, highlighting the effects of the size-reduction on the magnetic properties of the corresponding nanoparticles and hopefuly showcasing the importance of studying in the context of 2D limit the SCO phenomena.

The investigation and elaboration of the Spin-Crossover (SCO) phenomenon in Two – Dimensional (2D) Hofmann-type nanosized SCO materials and the size-reduction effect on cooperativity and thermodynamic properties of the nanoparticle are still in progress. Liquid Phase Exfoliation (LPE) as a top-down experimental protocol for the fabrication of 2D SCO atomically thin nanosheets is also an underexplored area of research. Given the increasing scientific interest for 2D nanosheets and their unique thickness-dependent electronic properties the above-mentioned study is of outmost importance. In this context, we present a detailed nano-synthetic study based on the reverse-micellar synthesis of [FeII(2-mpz)2Ni(CN)4] and a further rationalization of this method followed by LPE experimental protocols in order to synthesize nanoparticles with well-controlled size and shape. The role of concentration and reaction’s temperature is investigated in relation to the size, dispersion, morphology and magnetic properties of the nanoparticles. It was found that for specific values of these parameters the synthesis of nanoparticles is controlled and the final products are nanoparticles with an agglomerated architecture. According to an extensive Atomic Force Microscopy (AFM) Nano-topographic study, this agglomeration is best described as right truncated thick prisms of [FeII(2-mpz)2Ni(CN)4] stacked in a vertical position on a rectangular base plate. During the LPE procedure and by prolonging the sonication period the thick prisms are detached and, eventually, exfoliated to atomically thin right prism of height ~1 nm. Magnetic measurements revealed that the size reduction leads to the progressive downshift of abrupt thermal hysteresis with two-step SCO transition temperatures of the bulk [FeII(2-mpz)2Ni(CN)4] material to a gradual incomplete SCO behavior of an almost single layer 2D [FeII(2-mpz)2Ni(CN)4] nanosheet.

The 1 : 1 : 1 reaction of YbCl3·6H2O, K3[Co(CN)6] and bpyO2 in H2O has provided access to a complex with formula [YbCo(CN)6(bpyO2)2(H2O)3]·4H2O (1) in a very good yield while its structure has been determined by single-crystal X-ray crystallography and characterised based on elemental analyses and IR spectra. Magnetic susceptibility studies showed the complex to be a field induced single molecule magnet, as confirmed by μ-SQUID measurements. CASSCF calculations confirm the existence of a mJ = 7/2 ground state, with rather large transverse components, responsible for the fast relaxation characteristic of compound 1 at zero DC field, which is reduced upon application of DC fields. Moreover, a combination of luminescence studies along with CASSCF calculation allows the identification of the band structure of the complex, which is ultimately related to its electronic properties. Compound 1 operates as a luminescent thermometer in the 125-300 K range with a maximum relative thermal sensitivity of ≈0.1% K−1 at 180 K. published

The 1 : 2 reaction between Dy(O

The 1:1 reaction of trans-[ReIIICl3(PPh3)2(MeCN)] with 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol, H3L, in toluene gave the dinuclear complex [ReIII2Cl4(HL)(PPh3)]·2C7H8 (1·2C7H8), while the 1:2 reaction led to the formation of complex [ReIVCl2(HL)(PPh3)] (2). In both species, the Schiff-base ligand exists in its doubly deprotonated form, HL2–, forming chelate rings around the metallic centers. In addition, 1·2C7H8 displays a unique triple metal-to-metal bond between the two trivalent rhenium ions separated at a 2.229(1) A bond distance, while in complex [ReIVCl2(HL)(PPh3)] (2) the two aromatic ligands, HL2– and PPh3, occupy axial positions, with the terminal Cl– ions in the trans position. Investigation of the magnetic properties revealed a Curie paramagnetic behavior (S = 1/2) with a pronounced temperature independent paramagnetism (TIP) for 1·2C7H8 and 2. Both the geometry and the electronic structure of both compounds have been studied by means of density functional theory (DFT) calculations,...

This review is focused on the downsizing effect of a family of Hofmann-type Metal Organic Frameworks (MOFs) exhibiting Spin-Crossover Phenomenon (SCO) at high temperatures. Their nanoscale importan...

International audience; Celebrating the “25th Anniversary of Molecules” with a Special Issue dedicated to “Recent Advances in Inorganic Chemistry” strengthens the renewed role that inorganic chemistry, one of the oldest chemistry divisions, has lately earned thanks to cutting-edge perspectives and interdisciplinary applications, eventually receiving the veneration and respect which its age might require [...]

emperature-sensitive crystalline phases, pertaining to discrete clusters of binary and ternary Co(II,III):iminodipropanol:(N,N'-aromatic binder) systems, were prepared. The rich structural speciation of such systems in alcoholic media and their unique structural, magnetic, and spectroscopic profiles have been demonstrated. The need to understand the chemical reactivity of such complex ternary Co(II)-(1,1'-iminodi-2-propanol) systems, in the presence of N,N'-aromatic chelators 2,2'-bipyridine and 1,10-phenanthroline and aromatic binder 4,4'-bipyridine in methanol, led to the synthetic development of well-defined hybrid metal-organic materials with discrete spectroscopic, structural, electrochemical, and magnetic properties. The surprisingly plethoric family of the prepared mononuclear-trinuclear-tetranuclear Co(II,III) clusters was characterized through elemental analysis, FT-IR, and X-ray crystallography. Enrichment of their physicochemical profile originated from electrochemical, optical (UV/Vis, luminescence), magnetic, and EPR studies, unequivocally supporting their structural formulation. Collectively, the experimentally and theoretically (Bond-Valence-Sum, Hirshfeld) perused structures project the influence of molecular stoichiometry and temperature on targeted synthetic efforts toward crystal engineering of discrete Co(II,III)-center assemblies, exemplifying structure-reactivity correlations and magneto-optical-structural attributes.

While synthetic methods for the grafting of nanoparticles or photoactive molecules onto carbon nanotubes (CNTs) have been developed in the last years, a very limited number of reports have appeared on the grafting of single-molecule magnets (SMMs) onto CNTs. There are many potential causes, mainly focused on the fact that the attachment of molecules on surfaces remains not trivial and their magnetic properties are significantly affected upon attachment. Nevertheless, implementation of this particular type of hybrid material in demanding fields such as spintronic devices makes of utmost importance the investigation of new synthetic protocols for effective grafting. In this paper, we demonstrate a new experimental protocol for the noncovalent grafting of DyIII2 SMM, [Dy2(NO3)2(saph)2(DMF)4], where H2saph = N-salicylidene-o-aminophenol and DMF = N,N-dimethylformamide, onto the surface of functionalized multiwalled CNTs (MWCNTs). We present a simple wet chemical method, followed by an extensive washing protoc...

The interaction of Mn(II) with the non-steroidal anti-inflammatory drug mefenamic acid (Hmef) in the presence or absence of salicylaldoxime (H2sao) leads to the formation of the hexanuclear Mn(III) cluster [Mn6(O)2(mef)2(sao)6(CH3OH)4] 1, characterized as stepladder inverse-9-metallacrown-3 accommodating mefenamato ligands, or the mononuclear Mn(II) complex [Mn(mef)2(CH3OH)4], 2, respectively. Both complexes were characterized by physicochemical and spectroscopic techniques and the structure of complex 1 was characterized by X-ray crystallography. The overall magnetic behavior of compound 1 is antiferromagnetic with a high-spin well-isolated ground state S = 4. The in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs cisplatin and 5-fluorouracil. Furthermore, in silico predictive tools have been employed to study the properties and acute rat toxicity and cell line cytotoxicity of the most active complex.

Herein we report the synthesis, isolation and structural characterization of hybrid microporous Hofmann-like spin crossover polymers with the molecular formula {Fe(C4H4N2)[M(CN)4]}·(C4H4N2)·1.2H2O where M = Pt(II) (1), Pd(II) (2). Magnetic susceptibility studies showed well-resolved hysteretic three-step for 1 and two-step for 2 thermally induced spin transitions.

The diamagnetic two-dimensional Hofmann-type metal-organic framework [Zn

Interaction of Cu(NO3)2 with phenyl 2-pyridyl ketoxime (PhPyCNOH) in the presence or absence of sodium diclofenac (Nadicl) leads to the formation of mono- or double-decker trinuclear clusters, respectively, characterized as inverse-9-metallacrown-3 accommodating dicl– or NO3– anions. The structures of [Cu3(PhPyCNO)3(3-O)(NO3)]2 (1) and [Cu3(PhPyCNO)3(3-OH)(dicl)2]·MeOH·0.5H2O (2·MeOH·0.5H2O) were determined by X-ray crystallography. Magnetic studies show a large antiferromagnetic interaction, whereas a discrepancy appears between the low-temperature magnetic data and that predicted from an isotropic Hamiltonian model, indicating the influence of antisymmetric interactions. By using a different magnetic model with antisymmetric terms, the low-temperature susceptibility and magnetization data were fitted. The EPR data support the observation that 2 has isosceles or lower magnetic symmetry, whereas the antisymmetric exchange mechanism is used to identify the reported g values of the spectra. EPR studies also revealed that complex 2 keeps its structure in solution. The complexes interact with calf-thymus DNA by intercalation. The complexes, as well as [Cu2(dicl)4(H2O)2] (3), bind to albumins with relatively high binding constants. The highest cytotoxicity of the diclofenac compounds was observed after 24 h of incubation, whereas HL-60 cells recovered after 72 h of incubation in the presence of each compound. Moreover, complex 3 was the most cytotoxic among the compounds, and complex 2 was as cytotoxic as Nadicl.

While synthetic methods for the grafting of nanoparticles or photoactive molecules onto carbon nanotubes (CNTs) have been developed in the last years, a very limited number of reports have appeared on the grafting of single-molecule magnets (SMMs) onto CNTs. There are many potential causes, mainly focused on the fact that the attachment of molecules on surfaces remains not trivial and their magnetic properties are significantly affected upon attachment. Nevertheless, implementation of this particular type of hybrid material in demanding fields such as spintronic devices makes of utmost importance the investigation of new synthetic protocols for effective grafting. In this paper, we demonstrate a new experimental protocol for the noncovalent grafting of Dy

The reaction of [Cr3IIIO(OAc)6(H2O)3]NO3·AcOH with 2-hydroxynaphthaldehyde, 2-amino-isobutyric acid and NiCl2·6H2O in MeOH, under basic and solvothermal conditions, led to the formation of the quasi-1D coordination polymer {[CrIII2NiII(L)4(MeOH)2]}n (where L = the dianion of the Schiff base between 2-hydroxynaphthaldehyde and 2-amino-isobutyric acid), which behaves as a ferromagnetic chain, displaying slow relaxation of magnetization., ME thanks DIPC for the support of his stay at San Sebastián and MINECO for funding (MAT2015-68204-R). JML thanks the Excellence Unit ‘‘Maria de Maeztu’’ [MDM-2015-0538].

The interactions of MnII ions with the nonsteroidal anti-inflammatory drug sodium diclofenac in the presence of 1,10-phenanthroline and 2,2′-dipyridylamine lead to the formation of the trinuclear [Mn3(diclofenac)6(1,10-phenanthroline)2(MeOH)] (1) and the mononuclear [Mn(diclofenac)2(2,2′-dipyridylamine)] (2), respectively, which have been characterized by X-ray crystallography. Three different coordination modes of the diclofenac ligands exist in 1, whereas the bidentate chelating mode is observed in 2. In the initial evaluation of their biological properties and potential applications, the complexes exhibited good binding propensity to human or bovine serum albumin proteins and have relatively high binding constants. The ability of the compounds to scavenge 1,1-diphenylpicrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and hydroxyl radicals was evaluated, and 1 was the most-effective scavenger among 1, 2, and sodium diclofenac.

A series of CoFe2O4 nanoparticles were formed through a variant hydrothermal synthesis based on a self-assembled oil–water system in autoclaves at 200 °C in the presence of octadecylamine and the trivalent iron and cobalt acetylacetonates. The variation of the water content, the different valence of the cobalt precursors (Co(II) and Co(III)) as well as Fe:Co precursor ratios (2:1 and 1:1) were studied. CoFe2O4 nanoparticles with a size range of 9–16 nm of high crystallinity and enhanced saturation magnetization (∼89 emu g–1) have been isolated and characterized. Raman spectroscopy provided information concerning the lattice strain, while incorporation of Co2+ at Td sites of the spinel indicated a different inversion degree (0.67–0.60) among the samples. EPR studies showed that EPR signal and spin relaxation process were size dependent and influenced by aggregation effects. CoFe2O4 nanoparticles were converted to dual agents via a reaction between the free amine groups of the organic coating and the sulfon...

The interaction of Mn(ClO4)2·6H2O with salicylaldoxime (H2sao) in the presence of nonsteroidal anti-inflammatory drug (NSAID) sodium diclofenac (Nadicl) or indomethacin (Hindo) leads to the formation of the hexanuclear Mn(III) clusters [Mn6(O)2(dicl)2(sao)6(CH3OH)6] (1) and [Mn6(O)2(indo)2(sao)6(H2O)4] (2) both characterized as stepladder inverse-9-metallacrown-3 accommodating dicl- or indo- ligands, respectively. When the interaction of MnCl2·4H2O with Nadicl or Hindo is in the absence of H2sao, the mononuclear Mn(II) complexes [Mn(dicl)2(CH3OH)4] (3) and [Mn(indo)2(CH3OH)4] (4) were isolated. The complexes were characterized by physicochemical and spectroscopic techniques, and the structure of complexes 1 and 2 was characterized by X-ray crystallography. Magnetic measurements (dc and ac) were carried out in order to investigate the nature of magnetic interactions between the magnetic ions and the overall magnetic behavior of the complexes.

The synthesis, characterization, and magnetic behavior of a new Co7 disc [CoII4CoIII3(Htea)3(tea)3](NO3)2·2CH3OH·1.5H2O (1, H3tea = triethanolamine), which was isolated in high yield in the presence of only triethanolamine, is reported. Magnetic measurements confirmed that 1 belongs to the family of single-molecule magnets (SMMs), and this is the second example of a cobalt(II)-based complex with CoII4CoIII3 oxidation levels. A spin-coating method was used for the deposition of 1 on highly oriented pyrolytic graphite (HOPG) substrates. According to AFM/magnetic force microscopy (AFM/MFM) studies, molecular aggregates were deposited at the center of terraces in a homogeneous distribution. The obtained mean diameter was 21.2 ± 7.0 nm, and the mean height was 1.4 ± 0.5 nm. Assuming that the aggregates can be modeled as a spherical cap, a rough estimate of 74–263 molecules of 1 per aggregate is obtained.

Two new six-coordinated high-spin Co(II) complexes have been synthesized through the reactions of Co(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO2-saloH) or 3-methoxy-salicylaldehyde (3-OCH3-saloH) under argon atmosphere: [Co(dpamH)2(5-NO2-salo)]NO3 (1) and [Co(dpamH)2(3-OCH3-salo)]NO3·1.3 EtOH·0.4H2O (2). According to the crystal packing of compound 1, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N-H···O and C-H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π-π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound 2 reveals a 1D assembly consisting solely from the coordination cations, which is formed by π-π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N-H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2-300 K on the basis of an empirical expression which allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin S(eff) = 1/2. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound 2. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δr/k(B) = 55(1) K for the [10-1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character.

Chromium is widespread in the environment and is used in ample industrial applications in abiotic and biological systems. Its ability to influence biological processes through interactions with biomolecules underscores its positive role as well as its toxic manifestations in higher organisms. In an attempt to understand its (bio)chemistry, research efforts were undertaken to explore the aqueous chemistry of Cr(III) with the low molecular mass physiological ligand, quinic acid. pH-Specific synthesis in the binary Cr(III)–quinato system led to the isolation of Na[Cr3O(C7H11O6)6(H2O)3]·(NO3)1.5·(OH)0.5·6H2O (1). 1 crystallizes in the monoclinic space group C2, with a = 32.16(1) A, b = 14.076(7) A, c = 15.083(5) A, β = 95.53(1)°, V = 6796(5) A3, and Z = 4. The structure of 1 reveals a trinuclear assembly of Cr(III) with quinate. The assembly consists of a [Cr3O] core containing a triply bound oxido O2− ligand holding the three Cr(III) ions together and six coordinated quinato ligands linking contiguously the three Cr(III) centers in a peripheral cyclic fashion. Each ligand binds two abutting Cr(III) metal ions through the carboxylato oxygens. The alcoholic groups of the quinates are not deprotonated and do not coordinate to the Cr(III) ions. The collective binding of Cr(III) with quinates in a 1:2 ratio leads to a distorted octahedral geometry around each metal center, with the sixth coordination site occupied by a water ligand. 1 was characterized by elemental analysis, spectroscopic (UV–Vis, FT-IR, ESI-MS, EPR), structural, thermal, cyclic voltammetric, and magnetic susceptibility studies. The collective structural and spectroscopic techniques point out the distinct properties of 1 in the solid state and in solution, thus exemplifying the physicochemical profile of that compound in the overall structural speciation scheme of the binary Cr(III)–quinato system. Solid state-solution structural correlation suggests retention of the trinuclear core complex of 1 in solution, also supported by ESI-MS, thereby lending credence to the detailed aqueous speciation studies in the binary Cr(III)–quinato system investigated in the employed pH range. The unique behavior of 1 in comparison to other known trinuclear [Cr3O]-containing compounds (a) signifies the importance of binary interactions of Cr(III) with hydroxycarboxylic acids, and (b) necessitates further perusal of analogous binary systems of Cr(III), that will enable understanding of the factors influencing the role of the specific metal ion in the development of (bio)chemical reactivity in biological systems and abiotic materials applications.

Cobalt(II) complexes with the non-steroidal anti-inflammatory drug naproxen in the presence or absence of nitrogen-donor heterocyclic ligands (pyridine, 2,2′-bipyridine or 1,10-phenanthroline) have been synthesized and characterized with physicochemical and spectroscopic techniques. The deprotonated naproxen acts as monodentate ligand coordinated to Co(II) ion through a carboxylato oxygen. The crystal structure of [bis(aqua)bis(naproxenato)bis(pyridine)cobalt(II)], 2 has been determined by X-ray crystallography. The EPR spectrum of complex 2 in frozen solution reveals that it retains its structure. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and [(2,2′-bipyridine)bis(methanol)bis(naproxenato)cobalt(II)] exhibits the highest binding constant to CT DNA. The cyclic voltammograms of the complexes recorded in DMSO solution and in the presence of CT DNA in 1/2 DMSO/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that they can bind to CT DNA by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. Naproxen and its cobalt(II) complexes exhibit good binding propensity to human or bovine serum albumin proteins having relatively high binding constant values. The antioxidant activity of the compounds has been evaluated indicating their high scavenging activity against hydroxyl free radicals and superoxide radicals.

Cobalt is an abundant metal ion present in the abiotic and biological world. The chemical reactivity of Co(II) is exemplified through complex interactions with variable molecular mass ligands, including amino acids, peptides, variable nature organic ligands, and/or phospho(nate)-derivatives thereof. Poised to gain insight into the chemical reactivity of Co(II) toward the family of mixed (carboxy)phosphonate-containing ligands, pH-specific aqueous reactions were carried out between Co(II) and N,N-bis(phosphonomethyl)-glycine (NTA2P), leading to a new pH-structural variant species (NH4)3[Co(C4H6O8NP2)(H2O)2]·4H2O (1) at pH 8. Compound 1 was characterized analytically, spectroscopically (FT-IR, UV–Vis, EPR), and magnetically. X-ray crystallography reveals a mononuclear complex of Co(II) in an NO5 octahedral environment. The solid state magnetic and EPR data on 1 suggest the presence of a high-spin Co(II) in a distorted octahedral geometry, with a ground state of an effective spin S = 1/2. The solution UV–Vis and EPR data suggest retention of the integrity of 1, consistent with the magnetization measurements. Detailed aqueous speciation studies on binary Co(II)–carboxylate (NTA) and all Co(II)–(carboxy)phosphonate (NTAxP; x = 1–3) systems reveal the aqueous distributions of all species involved in the respective systems and project a mononuclear species not unlike that of 1 in the Co(II)–NTA2P system. The structural and chemical attributes of the title complex reflect the (a) pH-dependent chemical reactivity in the binary Co(II)–NTA2P system, and (b) structure–activity correlations in the aqueous media linking both high and low pH-structural variants. To this end, fundamental structural properties influence the reactivity of Co(II) toward phosphonate and mixed carboxyphosphonate ligands and are ultimately exemplified as a function of phosphonate-containing moieties in NTA derivatives. The variably configured species in such binary Co(II)–ligand systems define the pH dependence and nature of interactions between the two reagents, and could serve further as precursors in the design and discovery of new Co(II)–organophosphonate materials of specific structural lattice, spectroscopic, and magnetic properties.

Three new trinuclear copper(II) complexes, [(CuL1)(3)(mu(3)-OH)](ClO4)(2)center dot 3.75H(2)O (1), [(CuL2)(3)(mu(3)-OH)](ClO4)(2) (2) and [(CuL3)(3)(mu(3)-OH)](BF4)(2)center dot 0.5CH(3)CN (3) have been synthesized from three tridentate Schiff bases HL1, HL2, and HL3 (HL1 = 2-[(2-amino-ethylimino)-methyl]-phenol, HL2 = 2-[(2-methylamino-ethylimino)-methyl]-phenol and HL3 = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol). The complexes are characterized by single-crystal X-ray diffraction analyses, IR, UV-vis and EPR spectroscopy, and variable-temperature magnetic measurements. All the compounds contain a partial cubane [Cu3O4] core consisting of the trinuclear unit [(CuL)(3)(mu(3)-OH)](2+) together with perchlorate or fluoroborate anions. In each of the complexes, the three copper atoms are five-coordinated with a distorted square-pyramidal geometry except in complex 1, in which one of the Cu-II ions of the trinuclear unit is six-coordinate being in addition weakly coordinated to one of the perchlorate anions. Variable-temperature magnetic measurements and EPR spectra indicate an antiferromagnetic exchange coupling between the CuII ions of complexes 1 and 2, while this turned out to be ferromagnetic for complex 3. Experimental values have been fitted according to an isotropic exchange Hamiltonian. Calculations based on Density Functional Theory have also been performed in order to estimate the exchange coupling constants in these three complexes. Both sets of values indicate similar trends and specially calculated J values establish a magneto-structural correlation between them and the Cu-O-Cu bond angle, in that the coupling is more ferromagnetic for smaller bond angle values.

A new linear trinuclear nickel(II) complex, [Ni3(salme)2(OCn)4] (Hsalme = 2-[(3-methylamino-propylimino)-methyl]-phenol, OCn = cinnamate), showing weak ferromagnetic coupling (J = 1.8(1) cm−1) through phenoxo and a novel tridentate bridging mode (1κ2OO′:2κO′) of the cinnamate ligand has been synthesized and structurally characterized by X-ray crystallography.

Three new linear trinuclear nickel(II) complexes, [Ni-3(salpen)(2)(OAc)(2)(H2O)(2)]center dot 4H(2)O (1) (OAc = acetate, CH3COO-), [Ni-3(salpen)(2)(OBz)(2)] (2) (OBz=benzoate, PhCOO-) and [Ni-3(salpen)(2)(OCn)(2)(CH3CN)(2)] (4) (OCn = cinnamate, PhCH=CHCOO-), H(2)salpen = tetradentate ligand, N,N'-bis(salicylidene)-1,3-pentanediamine have been synthesized and characterized structurally and magnetically. The choice of solvent for growing single crystal was made by inspecting the morphology of the initially obtained solids with the help of SEM study. The magnetic properties of a closely related complex, [Ni-3(salpen)(2)(OPh)(2)(EtOH)] (3) (OPh = phenyl acetate, PhCH2COO-) whose structure and solution properties have been reported recently, has also been studied here. The structural analyses reveal that both phenoxo and carboxylate bridging are present in all the complexes and the three Ni(II) atoms remain in linear disposition. Although the Schiff base ligand and the syn-syn bridging bidentate mode of the carboxylate group remain the same in complexes 1-4, the change of alkyl/aryl group of the carboxylates brings about systematic variations between six- and five-coordination in the geometry of the terminal Ni(II) centres of the trinuclear units. The steric demand as well as hydrophobic nature of the alkyl/aryl group of the carboxylate is found to play a crucial role in the tuning of the geometry. Variable-temperature (2-300 K) magnetic susceptibility measurements show that complexes 1-4 are antiferromagnetically coupled (J = -3.2(1), -4.6(1). -3.2(1) and -2.8(1) cm(-1) in 1-4, respectively). Calculations of the zero-field splitting parameter indicate that the values of D for complexes 1-4 are in the high range (D = +9.1(2), +14.2(2), +9.8(2) and +8.6(1) cm(-1) for 1-4, respectively). The highest D value of +14.2(2) and +9.8(2) cm(-1) for complexes 2 and 3, respectively, are consistent with the pentacoordinated geometry of the two terminal nickel(II) ions in 2 and one terminal nickel(II) ion in 3. (C) 2009 Elsevier Ltd. All rights reserved.

The reaction of 1-hydroxybenzotriazole, btaOH, with nickel(II) acetate tetrahydrate, in the absence of an external base, has been investigated. The reaction of Ni(O2CMe)2 · 4H2O with one equivalent of btaOH in nPrOH leads to the the first structurally characterized tridecanuclear nickel(II) cluster and the biggest metal/btaOH or btaO− cluster discovered to date, [Ni13(OH)6(O2CMe)8(btaO)12(H2O)6(nPrOH)4] · 6.6H2O · 4(nPrOH) (1 · 6.6H2O · 4(nPrOH)). The centrosymmetric molecule contains the {Ni13(μ3-ΟΗ)6(μ3-ONNNR)12}8+ core (R– = C6H4–) and is characterized by competitive antiferromagnetic exchange interactions within its pentanuclear subunits containing the μ3-ΟΗ− bridges. The reaction of 1 with an excess of N 3 - ions in refluxing MeOH has led to the azido-bridged product [Ni13(N3)6(O2CMe)8(btaO)12(MeOH)10] (2), in which the spin frustration observed in 1 seems to disappear.

The employment of the di-2-pyridyl ketone [ ( py ) 2 CO ] / PhCO 2 - / N 3 - ligand combination in copper(II) chemistry has provided access to the hexanuclear cluster [Cu6(O2CPh)4(N3)2{(py)2CO2}2{(py)2C(OH)O}2] (1), and the coordination polymers [Cu4(O2CPh)2(N3)4{(py)2C(OMe)O}2]n (2) and [Cu2(O2CPh)(N3)2{(py)2C(OMe)O}]n (3). The structural type (cluster versus polymer) depends on the reaction solvent. Complex 1 has a [CuII6(μ3-OR′′)2(μ-OR′′)4]6+ core based on a central defective cubane unit and two additional CuII atoms across the missing edges. Complex 2 consists of zig-zag chains and complex 3 consists of extended 2D networks that adopt the herringbone architecture which is not based on T-shaped nodes. Cluster 1 is antiferromagnetically coupled with an S = 0 ground state.

The reaction of 1-hydroxybenzotriazole (btaOH) with Ni(O2CMe)4 · 4H2O in nPrOH has led to the [Ni13(OH)6(O2CMe)8(btaO)12(H2O)6(nPrOH)4] (1) cluster; compound 1 is the first structurally characterized tridecanuclear nickel(II) cluster and the biggest metal/btaOH or btaO− cluster discovered to date. The centrosymmetric molecule contains the {Ni13(μ3-OH)6(μ3-ONNNR)12}8+ core (R– = C6H4–) and is characterized by competitive antiferromagnetic exchange interactions within its pentanuclear subunits containing the μ3-OH− bridges. The reaction of 1 with an excess of N 3 - ions in refluxing MeOH has led to the azido-bridged product [Ni13(N3)6(O2CMe)8(btaO)12(MeOH)10] (2).

The synthesis, crystal structure, and magnetic properties of two trinuclear oxo-centered carboxylate complexes are reported and discussed: [Cr3(μ3-O)(μ2-PhCOO)6(H2O)3]NO3·4H2O·2CH3OH (1) and [Cr3(μ3-O)(μ2-PhCOO)2(μ2-OCH2CH3)2(bpy)2(NCS)3] (2). For both complexes the crystal system is monoclinic, with space group C2/c for 1 and P1/n for 2. The structure of complex 1 consists of discrete trinuclear cations, associated NO3- anions, and lattice methanol and water molecules. The structure of complex 2 is built only by neutral discrete trinuclear entities. The most important feature of 2 is the unusual skeleton of the [Cr3O] core due to the lack of peripheral bridging ligands along one side of the triangular core, which is unique among the structurally characterized (μ3-oxo)trichromium(III) complexes. Magnetic measurements were performed in the 2−300 K temperature range. For complex 1, in the high-temperature region (T > 8 K), experimental data could be satisfactorily reproduced by using an isotropic exchange ...

A recently developed experimental and theoretical procedure is used in order to calculate the magnitude and anisotropy of interaction between a lanthanide and a 3d-metal ion. The general formula of the molecular compounds is [Ln(H2O)3(dmf)4(μ-CN)Fe–(CN)5] · nH2O where 1 ⩽ n ⩽ 1,5 and dmf = N,N′-dimethylformamide, abbreviated as [LnFe] from now on. The main parts of this procedure are (a) the evaluation of the effective g-parameters of the lanthanide ion with the help of EPR measurements. (b) The use of dual mode EPR spectroscopy to define the anisotropic exchange interactions with the help of an anisotropic Hamiltonian model. (c) Use of the same magnetic model to fit magnetization and susceptibility data in order to verify the EPR findings. It was possible to define some trends concerning the exchange components of the [DyFe] dimer according to which the antiferromagnetic isotropic exchange constant is smaller than 4 cm−1 and the anisotropic components are [Dexc, Eexc] = [⩾6(1), 0.0] cm−1. Also for the case of [TmFe] and [YbFe] dimers the antiferromagnetic isotropic exchange constant is smaller than 0.3 cm−1 while the anisotropic components are [Dexc, Eexc] = [⩾12.0, 0.0] cm−1 and [Dexc, Eexc] = [0.4(1), 0.0] cm−1, respectively.

A recently introduced experimental and theoretical procedure is presented in order to calculate the magnitude and anisotropy of interaction between a lanthanide and a 3d-metal ion. The general formula of the hetero-one-dimensional molecular compounds is trans-[M(CN)4(μ-CN)2Ln(H2O)4(bpy)]n·nH2O · 1.5nbpy (M = Fe3+, Cr3+; Ln = Er3+, Yb3+), where bpy = 2,2′-bipyridine, abbreviated as [LnM] from now on. The main parts of this procedure are: (a) the evaluation of the effective g-parameters of the lanthanide ion with the help of EPR measurements; (b) the use of dual-mode EPR spectroscopy to define the anisotropic exchange interactions with the help of an anisotropic Hamiltonian model; (c) use of the same magnetic model to fit magnetization and susceptibility data in order to verify the EPR findings. It was possible to define some trends concerning the exchange components of the [ErCr] chain according to which the antiferromagnetic isotropic exchange constant is smaller than 0.7(1) cm−1 and the anisotropic components are [Dexc, Eexc] = [−0.4(1), 0.0(1)] cm−1. Also for the case of [YbCr] and [YbFe] chains the antiferromagnetic isotropic exchange constant is smaller than 0.1(1) cm−1 and 0.25(1) cm−1, respectively while the anisotropic components are [Dexc, Eexc] = [−0.3(1), 0.0(1)] cm−1 and [Dexc, Eexc] = [−0.1(1), 0.0(1)] cm−1, respectively.

An experimental and theoretical approach for the determination of the anisotropic exchange interaction constants in (Cu 2+ ,L n 3+ ) pairs where Ln = Tb 3+ ,D y 3+ is presented. According to this approach the same phenomenological anisotropic magnetic model was used to simulate the low temperature magnetic behaviour of the pairs as well as their EPR spectra in parallel and perpendicular mode. For the (Cu, Tb), [L 1 Cu(O2COMe)Tb(thd)2], (L 1 = N,N 0 -2,2-dimethylpropylenedi(3-methoxysalicylideneiminato; thd– = tetramethylheptanedionato)) and (Cu, Dy) complexes, [L 2 Cu-(Me2CO)Ln(NO3)3], (L 2 = N,N 0 -2-methyl-1,2-propylenedi(3-methoxysalicylideneiminato)), it has been found that the exchange interaction is ferromagnetic with the Jz interaction component larger than the other two terms

An experimental and theoretical procedure is introduced in order to calculate the magnitude and anisotropy of interaction between a lanthanide and a 3d-metal ion. The general formula of the molecular compounds is [Ln(H 2 O) 3 (dmf) 4 (μ-CN)Fe-(CN) 5 ] · n H 2 O, where 1 ⩽ n ⩽ 1,5 and dmf = N , N ′-dimethylformamide, abbreviated as [LnFe] from now on. The main parts of this procedure are (a) the evaluation of the effective g -parameters of the lanthanide ion with the help of EPR measurements; (b) the use of dual-mode EPR spectroscopy to define the anisotropic exchange interactions with the help of an anisotropic Hamiltonian model; (c) use of the same magnetic model to fit magnetization and susceptibility data in order to verify the EPR findings; and (d) introduction of a supportive technique, in our case Mossbauer spectroscopy due to the presence of the Fe ion. It was possible to define some trends concerning the exchange components of the [CeFe] dimer according to which the isotropic exchange constant is smaller than 2 cm −1 and the anisotropic components are [D, E] = [0.06(1), 0.05(1)] cm −1 . Using EPR spectrosopy it was possible to prove that the [PrFe] and [EuFe] dimers have negligible interactions. For the case of [PrFe], using appropriate magnetic models the energy difference between the ground state Γ 1 and the excited Γ 3 , Γ 4 and Γ 5 were calculated and found to be Δ 31 = 293(5) cm −1 , Δ 41 = 76(5) cm −1 and Δ 51 = 232(5) cm −1 . For the case of [EuFe], the spin–orbit coupling parameter was found to be λ = 340 cm −1 .

The iron complexes with the phenoxyalkanoic acids 3,4-D, 2,3-D and 2,4,5-T in the presence or not of a nitrogen donor heterocyclic ligand, phen, were prepared and characterized. Interaction of Fe(III) with phenoxyalkanoic acids and phen leads to dinuclear neutral complexes while the absence of phen favours trinuclear cationic or tetranuclear neutral forms. The crystal structure of hexakis(2,3-dichlorophenoxyacetato)tris(methanol)oxotri-iron(III) chloride–methanol(1/3), [Fe3O(2,3-D)6(MeOH)3]Cl · 3MeOH (2), and tetrakis(dimethyl-sulfoxide)octakis(2,4,5-trichlorophenoxyacetato)dioxotetra-iron(III) methanol(1/2)–water(1/1)–dimethylsulfoxide(1/0.8), {[Fe4O2(2,4,5-T)8(dmso)4] · 2MeOH · H2O · 0.8dmso} (3), have been determined and refined by least-squares methods using three-dimensional Mo Kα data. Magnetic data of the trimer show antiferromagnetic interaction. The ground state of the system is S = 1/2 with a small percentage of S = 5/2 paramagnetic impurity ρ = 0.7%. For the tetramer, the magnetic data suggest antiferromagnetically coupled system with S = 0 ground state, while for the dimer, {[Fe2OCl2(3,4-D)2(phen)2] · H2O · 3.5MeOH} a very strong antiferromagnetic exchange interaction between the two ions has been observed. The fitting results give an exchange interaction of J = 254.1 cm−1, with S = 0 ground state with a small amount of paramagnetic S = 5/2 impurity (ρ = 0.3%).

Classical Monte Carlo simulations (CMC) of the magnetic properties of a two-dimensional network containing Mn(II) ions with S = 5/2 ground-state spin have been carried out within the frame of an isotropic Heisenberg model. Analytical expression fitting the numerical simulations for the 2D trellis layer coupled-ladder configuration has been derived. With this empirical formula in hands, magnetic interactions between the magnetic ions can be extracted from the experimental data of this kind of network. A fit of the experimental data for the complex, namely Mn 2 (C 7 H 11 O 6 ) 4 ] n · n H 2 O ( 1 ) has been carried out and the following parameters were obtained; J 1 = 0.13(1) K being the interladder interaction, J = 0.45(1) K being the intraladder interaction, g = 1.99(1).

The presence of cobalt in biological systems has been associated with a variety of regulatory roles as an inorganic cofactor. Its involvement in (bio)chemical processes, where it contributes to the integrity of the physiology of humans, underscores its ability to promote (bio)chemistry with molecular targets of variable mass and biological properties. Given the fact that organic phosphonates are widespread substrates/ligands in biological fluids, we sought to investigate the relevant chemistry with CoII. With the organophosphonate ligand N,N-bis(phosphonomethyl)glycine (H5NTA2P) as the main metal ion binder, aqueous reactions with CoII were examined, ultimately leading to the isolation of the complex [Co(C4H9O8NP2)(H2O)2]·2H2O (1) at pH 1.5. This complex was characterized analytically, spectroscopically (FT-IR, UV/Vis, EPR), magnetically, and by cyclic voltammetry. X-ray crystallography shows that 1 is a compound with a molecular type of lattice. The complex consists of a mononuclear, octahedral CoII center coordinated by oxygen atoms belonging to the terminal phosphonate and carboxylate groups of H3NTA2P2–, the ligand nitrogen, and two bound water molecules. It should be emphasized that similar structural features have been observed in other metal organophosphonate lattices of materials with potential catalytic and chemical reactivity. The magnetic and EPR data for 1 suggest the presence of a high-spin octahedral CoII, with a ground state of an effective spin S = 1/2. The solution UV/Vis and EPR spectra suggest retention of the integrity of 1, which is consistent with the magnetization measurements in the solid state. Collectively, the data suggest a soluble CoII–organodiphosphonate species, not unlike those expected in bio-fluids containing the specific ligand or ligands structurally akin to H3NTA2P2–.The biological relevance of 1 to species in bio-fluids and the structural association with CoII–organophosphonate materials is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)