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Supramolecular tessellation represents a newly emerging powerful tool for constructing crystalline and quasicrystalline structural aesthetics with molecular polygons/planigons. In turn, expanding such 2-periodic tessellation as tectonic layer to 3-periodic architecture of frameworks, promises the sublimation from visual beauty for pure appreciation to sophisticated performance of porous materials for real application, enabling us to build macroscopic behavior at the molecular scale. With the above foresight, we introduce herein a new discovery that integrating supramolecular tessellation and pillared-layer strategy assembles supramolecular frameworks (SFs). The tectonic layers are based on rhombille tessellation of hydrogen-bondings between FeII molecular building blocks and interstitial water molecules, showing a rare kagome dual (kgd) net. Under this strategy, we first observed that a new zlg 3D topology was born by pillaring with kgd layer. These SFs offer potential channel/voids for guests’ respiration, inducing a reversible allosteric transformation from ligand substitution. The transformation alters significantly the spin state which was quantified by 57Fe Mossbauer spectroscopy, NMR, magnetic dilution and DFT calculations. These compounds show magnetic and chromatic bistability (see TOC), providing a broad scope towards multifuctional frameworks via multifarious supramolecular tessellation.

Reported herein the binding affinity between Human Serum Albumin and the DNA binding and cleavage activity of three copper(II) complexes, [Cu(phen)(o-van)ClO4] (1), [Cu(phen)(gly)]ClO4 (2) and [Cu(L1)2(H2O)2] (3) wherein 1 and 2 are synthesized with 1,10-phenanthroline (phen) and co-ligands (o-van: o-vanillin; gly: glycine) and 3 with a ligand 2-hydroxy-3-methoxybenzylidene-4H-1,2,4-triazol-4-amine (H1L1). Complex 2 crystallizes in monoclinic (P21/n) space group shows square pyramidal geometry. The complex 3 crystallizes in monoclinic (P21/a) space group. All the three complexes exhibit binding affinity towards the transport protein Human Serum albumin (HSA). Quantitative evaluation of the thermodynamics of interaction and the results obtained from fluorescence spectroscopy suggest that metal coordinated glycynate, o-vanillin and perchlorate groups have a major role to play in the binding process, the latter two being stronger in the binding of complex 1. The coordinated water in complex 3 also plays an important role in the binding, which makes binding of complex 3 with HSA stronger than that of complex 2. Experimental results indicate that the binding affinity of the complexes towards CT-DNA is in the order 1 > 3 > 2 implying that complex 1 binds stronger than complex 3 and 2.The DNA cleaving activity of all the three complexes was explored in the presence of reactive oxygen compound, H2O2. All the three complexes have primarily shown the DNA cleaving activity.

Epoxy-based intumescent coatings are effective solutions for protecting steel against fire. To design a successful product, it is, however, of primary importance to investigate its long-term durability. Some of these coatings do not resist accelerated aging conditions such as contact with salted water. One solution to overcome this drawback consists of applying a specific topcoat. In this work, various topcoats were applied on a model intumescent coating. Topcoats were shown to impact, under heating, the char expansion, char morphology, and char strength. The general trend is that the topcoats, before any aging exposure, improve the fire resistance behavior of the intumescent coatings. Most topcoats, however, do not limit penetration of salted water into the coating, thus affecting the intumescent properties. Only a silane-based topcoat was reported to trap or limit the diffusion of sodium and chlorine ions, thus protecting the underlying intumescent coating.

Intumescent coatings are the present-day state-of-art techniques to protect steel structures and other structural materials from fire hazards. Thermal insulation properties of such protective materials are normally deduced from standard fire tests, however, with least reference to char integrity and strength. This work proposes a simple and resourceful in situ experimental protocol to evaluate char strength of intumescent coatings on steel panels during hydrocarbon time–temperature fire test (at about 1200°C). It is based on in-process monitoring the physical integrity, mechanical stability, and thermal insulation capacity of fully developed char under a stream of air (airjet) before steel plate reaches its critical temperature. A bench-scale furnace designed in our laboratory to reproduce hydrocarbon fire scenario (UL1709) was upgraded to simulate air turbulence to impact the char strength. Silicone- and epoxy-based coatings on steel panels were tested under these conditions. Silicone-based coatings are found to have several interesting advantages over the latter. Furthermore, this protocol was extended to investigate the compositional influence on char strength in a set of silicon-based coatings.

Two precursors for coordination polymer design, namely ethyl-4H-1,2,4-triazol-4-yl-acetate (1) and 4-(4H-1,2,4-triazol-4-yl)L-propionic acid (2), were prepared via a transamination reaction followed by crystallization from MeOH. Single crystal X-ray data analysis revealed that 1 and 2 exhibit homochiral helical and 2D hydrogen bonded networks, respectively.

A thermochromic 1D spin crossover coordination (SCO) polymer [Fe(βAlatrz)3](BF4)2·2H2O (1·2H2O), whose precursor βAlatrz, (1,2,4-triazol-4-yl-propionate) has been tailored from a β-amino acid ester is investigated in detail by a set of superconducting quantum interference device (SQUID), 57Fe Mossbauer, differential scanning calorimetry, infrared, and Raman measurements. An hysteretic abrupt two-step spin crossover (T1/2 ↓=230 K and T1/2 ↑=235 K, and T1/2 ↓=172 K and T1/2 ↑=188 K, respectively) is registered for the first time for a 1,2,4-triazole-based FeII 1D coordination polymer. The two-step SCO configuration is observed in a 1:2 ratio of low-spin/high-spin in the intermediate phase for a 1D chain. The origin of the stepwise transition was attributed to a distribution of chains of different lengths in 1·2H2O after First Order Reversal Curves (FORC) analyses. A detailed DFT analysis allowed us to propose the normal mode assignment of the Raman peaks in the low-spin and high-spin states of 1·2H2O. Vibrational spectra of 1·2H2O reveal that the BF4 - anions and water molecules play no significant role on the vibrational properties of the [Fe(βAlatrz)3]2+ polymeric chains, although non-coordinated water molecules have a dramatic influence on the emergence of a step in the spin transition curve. The dehydrated material [Fe(βAlatrz)3](BF4)2 (1) reveals indeed a significantly different magnetic behavior with a one-step SCO which was also investigated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A conformationally flexible triazole-carboxylic acid ligand derived from an l-amino acid, namely, 4 H-1,2,4-triazol-4-yl-acetic acid (αHGlytrz), has been exploited to synthesize a structurally diverse and functionally intriguing metal-organic framework with CuSiF6. The crystal structure reveals a novel single-walled metal-organic nanotube (SWMONT), namely, {[Cu3(μ3-OH)(H2O)3(Glytrz)3]·SiF6·8H2O·X}∞ (1), (where X=disordered lattice water molecules) having a pore size as large as zeolites. Compound 1 was synthesized as crystals, as powder, or as layers by precipitation/electrodeposition. Mercury intrusion porosimetry demonstrates the ability of this material to store metallic mercury, after a pressure treatment, contrary to previous literature examples.

A classical Schiff base N,N′-bis(4-hydroxysalicylidene)ethylenediamine (L2), a member of the Salen group that has been introduced as a non-phosphorus and non-halogen flame retardant in thermoplastic polyurethane (TPU) is found to operate in an intriguing way to fire retard the material. L2 blended with TPU significantly improves the inherent flammability of TPU without a synergist. A plausible mechanism including intermediates in the reinforcement of this elastomer towards flame retardancy is elaborated in line with the char forming abilities of this β-resorcylaldehyde based Schiff base. Conclusions were drawn based on the input from thermal, spectroscopic, microscopic and operando spectroscopic techniques. While its un-substituted counterpart, N,N′-bis(salicylidene)ethylenediamine (L1) lags behind in performance, its structural isomer N,N′-bis(5-hydroxysalicylidene)ethylenediamine (L3) is equally efficient but exhibits another mechanism of action. The performance of L2-TPU is found to be mainly in a condensed phase and is due to decoding of intrinsic cross-linking ability of the key building block of the additive i.e. resorcinol via structural transformation over a range of temperature. This results in the methylene bridged phenolic resin type material having high temperature stability. The process is also found to interfere with TPU unzipping process delaying its thermal degradation and favoring extensive cross-linking promoting char formation with insulative properties.

An efficient catalytic system for the oxidation of alcohols has been developed by using iron(III) catalyst [Fe(phen) 2Cl 2]NO 3 (1) (phen = 1,10-phenanthroline) and H 2O 2 as terminal oxidant. A series of primary and secondary alcohols were oxidized into aldehydes and ketones in good yields and excellent selectivities after a short reaction time. The mononuclear iron(III) complex [Fe(phen) 2Cl 2]NO 3 was characterized by several independent methods. The X-ray structure shows distorted octahedral geometry around the Fe III center, which is in a high-spin state (S = 5/2) according to Mossbauer study. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Glass-fiber reinforced polyamide 66 is flame retarded with a mixture of melamine-poly(zinc phosphate), (Safire®400) and diethyl aluminium phosphinate. The performance of this synergistic combination of additives is multi-modal and a comprehensive investigation is undertaken to elucidate the underlying flame retardancy mechanism. The strategy was to characterize the different chemical species responsible for flame retardancy that are generated in gas and condensed phases under different fire scenarios. Following heat release rate (HRR) curve of flame retarded polyamide formulations obtained by mass loss calorimeter, samples in different stages of degradation are collected and investigated. Further flame retardants and formulations were degraded in tubular furnace whose temperature protocol relied on thermal degradation profile obtained from thermogravimetric analysis (TGA). In either case, species generated in condensed phase were studied by solid state nuclear magnetic resonance spectroscopy (magic angle spinning (MAS) NMR; 27Al, 31P and 13C), Fourier transform Infra-red spectroscopy (FTIR), X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and optical microscopy, whereas TGA coupled FTIR, and pyrolysis gas chromatography mass spectrometry (Py/GC/MS) were utilised to investigate species released in gas phase. Flame retardancy mechanism is elaborated based on the identification of the chemical species in both gas and condensed phases and their specific contributing role.

A higher analogue in the melamine polyphosphate family, melamine-poly(aluminium phosphate) (Safire®200), that has shown flame retardancy along with aluminium phosphinate in glass-fibre reinforced polyamide 66 was investigated to elucidate their mode of action. The mechanistic investigation is based on examining the chemical species formed in the condensed and gas phase under different fire scenarios. Samples at different stages of degradation were collected based on the heat release rate (HRR) curve of cone calorimetry and further analysed. Additionally, formulations and flame retardants were also pyrolysed at characteristic temperatures in a tubular furnace based on their thermogravimetric analysis (TGA) profile and investigated. A fire retardancy-quenching mechanism is mapped out on the basis of input from solid state nuclear magnetic resonance spectroscopy (MAS NMR; 27Al, 31P and 13C), Fourier transform Infra-red spectroscopy (FTIR), X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and optical microscopy on degraded samples. Gas phase analysis was studied by TGA coupled FTIR.

An integrated multicomponent molecule, Melamine-poly(aluminium phosphate) (Safire®200), its zinc and magnesium analogues namely Safire®400 and Safire®600 respectively were used as flame retardants for glass fiber reinforced polyamide 66 in combination with aluminium phosphinate. Characterisation, thermal stability, combustion properties, glow-wire flammability index and glow-wire ignition temperature and cone calorimetry results are reported. Lower threshold of loading of flame retardants that pass V0 rating in UL-94 vertical burning test have been determined. Effect of Zinc borate (Firebrake®500 grade) in these formulations was investigated. Influence of additives on endothermic and exothermic transitions of polyamide 66 in these formulations were studied by differential scanning calorimetry. The formulations were evaluated against the properties and fire performances of classical commercial combination of aluminium phosphinate and melamine polyphosphate. All the new formulations down to 15% of additives loading achieve V0 rating according to UL-94 protocol. This synergistic combination of additives significantly reduces the peak of heat release rate (pHRR) and total heat release (THR) in formulations exhibiting various degrees of intumescence.

The spin transition properties of [Fe(fletrz)3](BF4)2•2H2O are described. Fletrz (4-(2’-fluoroethyl)-4H-1,2,4-triazole) is a novel fluorine substituted 1,2,4-triazole ligand which forms 1D chain upon self-assembly with FeII ions. This coordination polymer exhibits reversible abrupt thermochromic spin transition that has been probed by SQUID magnetometry, variable temperature 57Fe Mossbauer spectroscopy (77–300 K) and differential scanning calorimetry (100–300 K).

A new family of one-dimensional Fe(II) 1,2,4-triazole spin transition coordination polymers for which a modification of anion and crystallization solvent can tune the switching temperature over a wide range, including the room temperature region, is reported. This series of materials was prepared as powders after reaction of ethyl-4H-1,2,4-triazol-4-yl-acetate (αEtGlytrz) with an iron salt from a MeOH/H2O medium affording: [Fe(αEtGlytrz)3](ClO4)2 (1); [Fe(αEtGlytrz)3](ClO4)2·CH3OH (2); [Fe(αEtGlytrz)3](NO3)2·H2O (3); [Fe(αEtGlytrz)3](NO3)2 (4); [Fe(αEtGlytrz)3](BF4)2·0.5H2O (5); [Fe(αEtGlytrz)3](BF4)2 (6); and [Fe(αEtGlytrz)3](CF3SO3)2·2H2O (7). Their spin transition properties were investigated by (57)Fe Mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and differential scanning calorimetry (DSC). The temperature dependence of the high-spin molar fraction derived from (57)Fe Mössbauer spectroscopy in 1 reveals an abrupt single step transition between low-spin and high-spin states with a hysteresis loop of width 5 K (Tc(↑) = 296 K and Tc(↓) = 291 K). The properties drastically change with modification of anion and/or lattice solvent. The transition temperatures, deduced by SQUID magnetometry, shift to Tc(↑) = 273 K and Tc(↓) = 263 K for (2), Tc(↑) = 353 K and Tc(↓) = 333 K for (3), Tc(↑) = 338 K and Tc(↓) = 278 K for (4), T(↑) = 320 K and T(↓) = 305 K for (5), Tc(↑) = 106 K and Tc(↓) = 92 K for (6), and T(↑) = 325 K and T(↓) = 322 K for (7). Annealing experiments of 3 lead to a change of the morphology, texture, and magnetic properties of the sample. A dehydration/rehydration process associated with a spin state change was analyzed by a mean-field macroscopic master equation using a two-level Hamiltonian Ising-like model for 3. A new structural-property relationship was also identified for this series of materials [Fe(αEtGlytrz)3](anion)2·nSolvent based on Mössbauer and DSC measurements. The entropy gap associated with the spin transition and the volume of the inserted counteranion shows a linear trend, with decrease in entropy with increasing the size of the counteranion. The first materials of this substance class to display a complete spin transition in both spin states are also presented.

Mind the gap: A complete, cooperative spin transition for a mononuclear MnIII complex is reported with an 8 K hysteresis window. Raman spectra collected at a single temperature in warming and cooling modes confirm the electronic bistability within the hysteresis loop. The source of the cooperativity is a disconnection in the hydrogen-bonded 1D chains that connect adjacent cations owing to an order-disorder transition in the PF 6 - counterion. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A series of four FeII coordination polymers [Fe(patrz)3]Cl2•2H2O, [Fe(patrz)3]Cl2, [Fe(batrz)3]Cl2•2H2O and [Fe(batrz)3]Cl2 was prepared with slight variations in the ligand framework (1,2,4-triazol-4-yl-propanoic acid (patrz) or 1,2,4- triazol-4-yl-butanoic acid (batrz)) and solvation (2H2O or dry). Dramatic influence of chain length and solvent has been evidenced on magnetic properties. Spin crossover properties were carefully studied by temperature dependent SQUID magnetometry and 57Fe Mossbauer spectroscopy. Thermodynamic parameters for [Fe(batrz)3]Cl2•2H2O were determined by differential scanning calorimetry (DSC) allowing a simulation of the spin crossover behaviour and the quantification of the cooperativity.

New N-salicylidene meta and para aminobenzenesulfonate anions (1 and 2) presenting both reversible thermochromic properties and high thermal stability have been synthesized. These functional organic components have been successfully inserted into inorganic cationic [Cu II(phen) 3] and [Ni II(phen) 3] frameworks, as a proof of concept, affording [Cu(phen) 3](1) 2 (C 1), [Ni(phen) 3](1) 2 (C 2), [Cu(phen) 3](2)Cl·5H 2O·2CH 3CH 2OH (C 3) and [Ni(phen) 3](2)Cl·7H 2O·CH 3OH (C 4), that have all been structurally characterized by single crystal X-ray diffraction. Temperature dependent fluorimetry demonstrates, for the first time, that keto-enol tautomerization of the anion is effective in the organic-inorganic hybrid materials, even though no thermochromism is observed. This insertion method paves the way towards the synthesis of a panel of hybrid multifunctional materials. © 2011 Elsevier B.V. All rights reserved.

The spin crossover behaviour of a new class of FeII coordination polymers [Fe(phtptrz)3]I2 (1), [Fe(phtptrz)3](ReO4)2•CH3OH (2) and [Fe(phtptrz)3]TaF7•6H2O (3) based on a novel ligand 4-(3′ -N-phtalimido-propyl)-1,2,4-triazole (phtptrz), were investigated by temperature dependent 57Fe Mossbauer spectroscopy and magnetic susceptibility measurements. The adverse effect of bulky substituent on 1,2,4-triazole, favorable supramolecular interactions and influence of increasing anion size on spin crossover profile is discussed. 1 and 2 show thermally induced spin conversions of gradual and incomplete nature with associated thermochromism, and transition temperatures T1/2 ~ 163 K and 137 K, respectively. A spin state crossover is also identified for 3.

A series of 1D coordination polymers [Fe(patrz)3]X2·solv, (patrz = 1,2,4-triazol-4-yl-propanoic acid; X = BF\(_{4}^{-}\), ClO\(_{4}^{-}\), Cl − , NO\(_{3}^{-}\) and solv = MeOH or H2O) were precipitated from methanol. Their spin crossover properties were studied by temperature dependent SQUID magnetometry and 57Fe Mossbauer spectroscopy, both for solvated and desolvated complexes. Compounds show gradual incomplete spin crossover with distinct thermochromism, in particular [Fe(patrz)3](BF4)2·MeOH, for which only 27% of FeII ions are switched to the low-spin state at 77 K, as determined by a detailed 57Fe Mossbauer study. Other prominent features of this work are the interesting self assembly of 1D chain with exclusively triazole coordination from patrz ligand despite its ditopic nature and a hysteretic room temperature spin crossover in [Fe(patrz)3]Cl2.

An illustrious complex [Fe(ptz)6](BF4)2 (ptz = 1-propyl-tetrazole) (1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by 57Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a ~5% enriched [57Fe(H2O)6](BF4)2 salt on this membrane.

A tiny supramolecular synthon, 4H-1,2,4-triazol-4-yl acetic acid (HGlytrz) which is bifunctional by design having an electronic asymmetry and conformational flexibility has been introduced to synthesize iron(II) complexes. Having 1,2,4-triazole or carboxylic extremities on the same framework HGlytrz could display dual functionality by acting as a neutral as well as anionic ligand based on the possibility of deprotonation of carboxylic group. Four new iron(II) HGlytrz complexes with ClO\(_{4}^{-}\) (1), NO\(_{3}^{-}\) (2), BF\(_{4}^{-}\) (3) and CF3SO\(_{3}^{-}\) (4) anions were prepared. Formulation of their composition which is complicated due to ligand deprotonation is discussed. Unlike its ester protected counterpart ethyl-4H-1,2,4-triazol-4-yl-acetate (αGlytrz) which show hysteretic room temperature spin crossover, 1–4 remain in the high-spin state as revealed by 57Mossbauer spectroscopy. Prospects of such 1D coordination polymers with dangling unbounded carboxylic entities in the realm of self-assembled monolayer (SAM) are discussed.

A new 1D coordination polymer [Fe(βAlatrz)3](ClO4)2 ∙ H2O (1) with a neutral bidentate ligand, βAlatrz = 4H-1,2,4-triazol-4-yl-propionate, was prepared and its magnetic behavior was investigated by temperature dependent magnetic susceptibility measurements and 57Fe Mossbauer spectroscopy. The temperature dependence of the high-spin molar fraction derived from 57Fe Mossbauer spectroscopy recorded on cooling below room temperature reveals a gradual single step transition with T1/2 = 173 K between high-spin and low-spin states in agreement with magnetic susceptibility measurements. 1 presents striking reversible thermochromism from white, at room temperature, to pink on quench cooling to liquid nitrogen. The phase transition is of first order as deduced from differential scanning calorimetry, with T1/2 matching the one determined by both SQUID and 57Fe Mossbauer spectroscopy. A brief assessment has been made among closely related 1D coordination polymers to perceive the effect of ligand spacer length and anion effect on the spin crossover behavior of these new materials.

The perceptible appearance of biomolecules as prospective building blocks in the architecture of coordination polymers (CPs) and metal-organic frameworks (MOFs) are redolent of their inclusion in the synthon/tecton library of reticular chemistry. In this frame, for the first time a synthetic strategy has been established for amine derivatization in amino acids into 1,2,4-triazoles. A set of novel 1,2,4-triazole derivatized amino acids were introduced as superlative precursors in the design of 1D coordination polymers, 2D chiral helicates and 3D metal-organic frameworks. Applications associated with these compounds are diverse and include gas adsorption-porosity partitioning, soft sacrificial matrix for morphology and phase selective cadmium oxide synthesis, FeII spin crossover materials, zinc-b-lactamases inhibitors, logistics for generation of chiral/non-centrosymmetric networks; and thus led to a foundation of a new family of functional CPs and MOFs that are reviewed in this invited contribution.

The first crystal structures of a dinuclear iron(II) complex with three N1,N2-1,2,4-triazole bridges in the high-spin and low-spin states are reported. Its sharp spin transition, which was probed using X-ray, calorimetric, magnetic, and (57)Fe Mossbauer analyses, is also delineated in the crystalline state by variable-temperature fluorimetry for the first time.

N-4H-1,2,4-Triazol-4-yl-guanidine hydrochloride (L1) and a heterocyclized 3,4-diamino-4H-1,2,4-triazole hydrochloride (L2) were synthesized in good yields thanks to a transamination reaction of aminoguanidine and diaminoguanidine hydrochlorides, whose mechanism is presented. L1 and L2 crystallize in monoclinic (P21/a) and triclinic (P1) space groups, respectively. Hydrogen bonding interactions dictated by H-donor, acceptor rich ligand framework together with lattice chloride ions in L1 and L2 organize the crystal packing into a three-dimensional (3D) supramolecular network. The crystal structure of L1 is the first one for a 1,2,4-triazole ligand constructed from aminoguanidine. Both L1 and L2 that exist in monocationic form were introduced as supramolecular synthons to prepare Zn(II) complexes. Scanning electron microscopy (SEM) images on a bulk sample of [Zn(L1)2Cl2]Cl2·H2O (1) reveals a spontaneous aggregation of porous balls of coccolith morphology with surface decorated sickle-shaped particles of 100 nm thickness, whereas a powder sample of [Zn(L2)2Cl2]·H2O (2) shows neat rectangular blocks of 470 nm thickness. Colorless crystals of 2 crystallize in a monoclinic space group (C2/c). Zn(II) ions bound chloride with NH6B···Cl(1) = 2.495(2) A and N···H type bonding (N6···H3C3 = 2.743(2) A; N2···H7N7 = 1.989(2) A) affording a 3D supramolecular network. The degree of pyramidality, ΣN = 38°, observed at one of the terminal amines in L2 is still retained in 2, but “flipping” of orientation of attached protons due to directional H-bonding is observed too. Porosity partitioning by mercury porosimetry measurements on 1 and 2 reveals interparticular porosities between 7 and 15 μm. N2(g) and H2(g) gas adsorption capacities of 1 and 2 were measured by BET which shows no preference for N2(g) but a low irreversible H2(g) uptake of 3 cm3/g.

A detailed investigation on the properties of the high-temperature and low-temperature modifications of the iron(II) spin-crossover complex [FeL1(HIm)2] (1) and its isotopic deuterium-labelled analogue [FeL1(DIm)2] (1D), and the pair [FeL2(azpy)]·MeOH/[FeL2(azpy)]·CD3OD/[FeL2(azpy)] (2·MeOH/2·CD3OD/2), in which L1 and L2 are tetradentate N2O22–-coordinating Schiff base like ligands, L1 = {diethyl(E,E)-2,2′-[1,2-phenylbis(iminomethylidyne)]bis[3-oxobutanoate](2–)-N,N′,O3,O3′}, L2 = {2,2′-[1,2-phenylbis(iminomethylidyne)]bis[1-phenylbutane-1,3-dione](2–)-N,N′,O3,O3′},HIm = imidazole, and azpy = 4,4′-azopyridine, is presented. All complexes except 2 show a cooperative spin transition with hysteresis widths between approximately 5 K (1LT and 1LTD), 70 K (1HT[9] and 1HTD, around room temperature), and 80 K (2·MeOH and 2·CD3OD). In all cases, an influence of the H/D exchange on the transition temperature and the hysteresis width is observed. For 1HT, first-order reversal curves (FORCs) have been recorded, and a statistical analysis gives the interaction parameter J = 560 K, indicating strong intermolecular interactions. X-ray structural analysis of the different samples (1HT[9] and 1HTD: HS; 1LT and 1LTD: LS; and 2·MeOH and 2·CD3OD: HS) gives a deeper insight into the molecular packing in the crystals and helps explain the increase of cooperative interactions during the spin transition. In all cases, one hydrogen bond involves an oxygen atom of the Schiff base like ligand that serves as a donor for the iron centre. The influence of this hydrogen bond on the ligand field strength of the iron centre is discussed and a new model is developed to explain the observed connection between hydrogen bonds and exceptionally wide hysteresis loops for the complexes presented in this work and other examples from the literature.

Solvothermal and classical synthesis with an identical recipe involving 4H-1,2,4-triazol-4-yl acetic acid (HL1) and CdCl2 afforded two-dimensional (2D) (1)l and one-dimensional (2) coordination polymers, respectively. Hexagonal plate-like crystals of [Cd-2(L1)(2)Cl-2] (1), which crystallize in the chiral orthorhombic space group (P2(1)2(1)2(1)), were obtained in high yield. The 1,2,4-triazole-4-yl acetate (Li? ligand, which has a significant kink in the spacer, leads to the formation of a Cd-II complex displaying a 2D single-stranded helical array. The pitch height of the helix is equal to the length of the crystallographic a axis (7.579 angstrom) which comprises two cadmium atoms and two ligands. Solid-state emission of 1 shows a strong emission band around 465 nm with photoexcitation at 290 nm. Mercury porosimetry measurements reveal pore size distribution with a diameter of 80, 10, and 1 mu m. BET shows no preference for N-2(g) but a low H-2(g) adsorption of 4 cm(3)/g. Complex 1, which is constituted by a "soft" nonaromatic network that begins to collapse around 170 C, was subjected to controlled pyrolysis to produce CdO with morphology and phase selectivity. Texture of the thus obtained pure cubic phase of CdO (beta-form) was further tuned with the regulation of the annealing temperature. Crystals of rectangular blocks of [Cd(HL1L1)Cl]center dot 2H(2)O (2), which were formed in small quantity, feature a centrosymmetric, monoclinic space group (P2(1)/c). Their crystal structure reveals a one-dimensional linear chain where Cd atoms are connected by a triple bridge made up of one mu-chloride and two mu-N1,N2-1,2,4-triazole HL1 and L1. The coordination polymer charge is balanced by both chloride and the carboxylate group of L1.

The coordination compound Fe(BM-4-PTP) 2 (NCS) 2 ⋅2MeOH ( 1 ) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl-5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5–293 K) and pressure range (1 bar–12 kbar) by magnetic susceptibility measurements and variable temperature 57 Fe Mossbauer spectroscopy. The photo-induced colour change is accompanied by a distinct magnetic variation at room temperature. Potentialities of this functional optical material for display and data recording are introduced.

Coordinating abilities of 4R-1,2,4-triazole derivatives (R = glycine ethyl ester (L1), glycine (L2), diethylamino malonate (L3), methionine (L4) and diethyl aminomethylphosphonate (L5)) towards Zn-II ions have been studied in solution, in solid state and versus three zinc-beta-lactamases. The crystal structure of [Zn-3(L-4)(6)(H2O)(6)] (6) is described; it is the first crystal structure involving a 1,2,4-triazole functionalized methionine. It forms a trinuclear complex with central zinc octahedrally coordinated by only L4, whereas terminal zinc ions coordination sphere is completed by three water molecules. L4 exhibits a dual functionality of a bridging bidentate ligand as well as an anion. A dense hydrogen bonding network connects these trinuclear entity into a 3D supramolecular network. The Zn-II ions in 6 are held at equidistance (3.848 angstrom) which coincidently matches with the corresponding Zn center dot center dot center dot Zn distance in the binuclear zinc enzyme from Bacillus cereus (3.848 and 4.365 angstrom). Among L1-L5 screened for beta-lactamase assay, L4 shows modest inhibition for BcII enzyme. (C) 2010 Elsevier B.V. All rights reserved.

The thermally induced hysteretic spin transition (ST) that occurs in the polymeric chain compound [Fe(NH2trz)3](NO3)2 (1) above room temperature (Tc↑ = 347 K, Tc↓ = 314 K) has been tracked by 57Fe Mossbauer spectroscopy, SQUID magnetometry, differential scanning calorimetry (DSC), and X-ray powder diffraction (XPRD) at variable temperatures. From the XRPD pattern indexation, an orthorhombic primitive cell was observed with the following cell parameters: a = 11.83(2) A, b = 9.72(1) A, c = 6.361(9) A at 298 K (low-spin state) and a = 14.37(2) A, b = 9.61(4) A, c = 6.76(4) A at 380 K (high-spin state). The enthalpy and entropy variation associated to the ST of 1, have been evaluated by DSC as ΔH = 23(1) kJ mol−1 and ΔS = 69.6(1) J mol−1 K−1. These thermodynamic data were used within a two-level Ising like model for the statistical analysis of First Order Reversal Curve (FORC) diagram that was recorded for 1, in the cooling mode. Strong intramolecular cooperative effects are witnessed by the derived interacti...

Glycine ethyl ester was recruited in an amine exchange process based on a transamination to afford ethyl 4H-1,2,4-triazol-4-yl-acetate (L1). The acid hydrolysis of this molecule leads to quantitative isolation of 4H-1,2,4-triazol-4-yl acetic acid (L2). This versatile synthon crystallizes in a noncentrosymmetric orthorhombic space group (Fdd2) with Z = 16. This crystal structure is the first one for a 1,2,4-triazole ligand constructed from an amino acid derivative. The strong intermolecular hydrogen bonding O-HN (2.570(3)Å) connects molecules into infinite one-dimensional chains running parallel to the b axis, and the structure is further extended by numerous but moderate strength hydrogen bonds (C-HO). Prominent features of L2 are the presence of diverse potential coordinating groups such as carboxylic acid and triazole on the same framework as well as the inherent flexibility of the ligand backbone. Reaction of L1 or L2 with aq. Cu(BF4) 2 in aq. DMF gives dark blue crystals which crystallize in a noncentrosymmetric, cubic space group (I4̌3m) and which were formulated as [Cu3(μ3-O)(L2)3(H2O) 3]BF4H2O (C1). The self-assembly of C 3-symmetric, μ3-oxo bridged triangular tricopper secondary building blocks (SBB) formed an unique architecture which encompasses voluminous nanoball voids of 1 nm. The total solvent accessible volume is 4477.5 Å 3 which accounts for 48% of the cell volume. The crystal network stability was studied by thermogravimetric analysis (TGA)'differential thermal analysis (DTA) and scanning electron microscopy (SEM) analyses. Sorption properties and gas storage capacities were measured by BET. C1 shows no preference for N2(g), but a reversible H2(g) uptake of 21 cm3/g was observed. Morphology analysis by SEM on single crystals of C1 shows "ultrawellś of square shape irregularly located on the surface, whose origin is due to desolvation or crystal defects. Mercury porosimetry measurements reveal pore size distribution with a diameter ranging from 350 nm to 2.3 μm

A supramolecular engineering approach has been developed for a novel family of N-salicylidene aniline derivatives to control their thermo- and photochromic behaviours. Hsaltrz, Habs, Hsalphen, Hsaltz and Ksaltz are versatile molecules built from N-heterocycles, which, drive the molecular arrangement to form a controlled crystal packing with predesigned optical properties. A complete structural, optical and computational study of powders of these new molecular nanoswitches is presented. An N-salicylidene aniline derivative possessing no thermo- or photoinduced chromic properties thanks to a specific molecular geometry was sought, and Habs and Hsalphen were designed to enhance π-π stacking interactions. A theoretical study of the crystal packing, combined with time-dependent diffuse reflectance studies of Habs, have confirmed the appearance of photochromism at room, temperature completed with an unprecedented "spring-type effect" observed, during the photochemical relaxation of the metastable irans-keto form. The absence of thermochromism in an N-salicylidene aniline derivative, induced by the absence of cis-keto form, is a unique behaviour, firstly identified and explained, for these types of compounds. Finally, Hsaltz and Ksaltz are the result of a molecular derivation of Hsaltrz which allow enhancing the amplitude of thermochromism of these functional materials.

Imaging nano-domains in spin crossover (SCO) compounds remains so far an unreached goal. We report on the first AFM tapping-mode investigation of SCO single crystals, performed at room temperature with the well known mononuclear compound [Fe(ptz)(6)](BF4)(2) (ptz = 1-propyl-tetrazole) and the trinuclear supramolecular compound [Fe-3(hyetrz)(6)(H2O)(6)](CF3SO3)(6) (hyetrz = 4-(2’-hydroxyethyl)-1,2,4-triazole) which shows a gradual spin conversion centred at room temperature. The natural surface of the former crystal revealed a volatile coating of the scanned area attributed to the transport of adsorbed water under the effect of interaction with the AFM tip. The second one showed astonishing leopard-skin patterns assigned to the effect of atmospheric humidity on this hygroscopic compound. Their origin is discussed. We suggest the use of fluid coating layers as a general method for revealing the nano-patterning of physical properties (e.g. like-spin domains) at the surface of dielectric materials. [GRAPHICS] AFM-tapping images of [Fe-3(hyetrz)(6)(H2O)(6)](CF3SO3)(6) room temperature and ambient atmosphere. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The relationships between the crystal structure and optical properties of switchable N-salicylideneanils have been revised and discussed on the basis of new experimental results and a computational approach. N-salicylidene-3-aminopyridine (L(3)) is a versatile thermo- and photochromic molecule. It also exhibits an infinitely slow thermal back relaxation (k = 9.9x10(-8) s(-1)) after photoswitching that is suitable for optical memories. Contrary to reports in the literature, N-salicylidene-4-aminopyridine (L(4)) is exclusively thermochromic. To explain these unexpected optical properties in the solid state, crystallography combined with UV-visible spectroscopic data was exploited. L(3) was also used as a ligand in new thermochromic coordination complexes [M(CH(3)OH)(2)(L(3))(2)(NCX)(2)], in which M(II) = Fe, Co, Ni, Cu or Mn and X = S or Se (1-6), which allowed the fine-tuning of the electron density in the photochromic moiety. The influence of the coordination through the nitrogen of the pyridine ring is also fully discussed.

A facile one-step procedure for the preparation of 4,4'-bis-1,2,4-triazole is reported. Direct transamination of N,N-dimethylformamide azine dihydrochloride by heating with 4-amino-1,2,4-triazole in refluxing benzene readily yields the target molecule in short duration of time with significant yield (73%). This catalyst-free method was extended to synthesise a series of 4-substituted 1,2,4-triazoles of potential interest in coordination chemistry.

A broad spectrum of applications of "Salen"-based Schiff bases tagged them as versatile multifunctional materials. However, their applicability is often bounded by a temperature threshold and, thus, they have rarely been used for high temperature applications. Our investigation of a classical Schiff base, N,N'-bis(4-hydroxysalicylidene)ethylenediamine (L2), reveals that it displays an intriguingly combative response to an elevated temperature/fire scenario. L2 resists and regulates thermal degradation by forming an ablative surface, and acts as a thermal shield. A polycondensation via covalent cross-linking, which forms a hyperbranched cross-linked resin is found to constitute the origin of the ablative surface. This is a unique example of a resin formation produced with a Schiff base, that mimicks the operational strategy of a high-heat resistant phenolic resin. Further applicability of L2, as a flame retardant, was tested in an engineering polymer, polyamide-6. It was found that it reinforces the polymer against fire risks by the formation of an intumescent coating. This paves the way for a new strategic avenue in safeguarding polymeric materials toward fire risks. Further, this material represents a promising start for thermal protective applications.

Six ternary copper(II) complexes of general formulation [CuLB] (1-6), where L is dianionic ONS-donor thiosemicarbazones derived from the condensation of salicylaldehyde with thiosemicarbazides and B is NN-donor heterocyclic bases like 2,2'-bipyridine, 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline, are prepared from a reaction of copper(II) acetate hydrate with the heterocyclic base (B) and the thiosemicarbazone (H2L) in MeOH, and structurally characterized by X-ray diffraction technique. Crystal structures of the complexes display a distorted square-pyramidal (4 + 1) coordination geometry having the ONS-donor thiosemicarbazone bonded at the basal plane. The chelating heterocyclic bases exhibit axial-equatorial mode of bonding. The complexes are one-electron paramagnetic and they show axial X-band EPR spectra in DMF-toluene glass at 77 K giving g(parallel to)(A(parallel to)) and g(perpendicular to) values of similar to2.2 (175 x 10(-4) cm(-1)) and similar to2.0 indicating a {d(x2-y2)}(1) ground state. The complexes show a d-d band near 570 nm and a charge transfer band near 400 nm in DMF. The complexes are redox active and exhibit a quasireversible Cu(II)-Cu(I) couple in DMF-0.1 M tetrabutylammonium perchlorate near 0.1 V vs. SCE. They are catalytically active in the oxidation of ascorbic acid in presence of dioxygen. The complexes with a CuN3OS coordination model the ascorbate oxidation property of dopamine beta-hydroxylase and peptidylglycine a-hydroxylating monooxygeanase. (C) 2003 Elsevier Science B.V. All rights reserved.

The preparation of a novel pentadentate binucleating compartmental ligand, 2-hydroxy-5-methylisophthalaldehyde bis(p-methoxy thiobenzoylhydrazone), is described together with the corresponding chloro-bridged cobalt(II), nickel(II), copper(II) and zinc(II) complexes, which were characterized based on spectral, magnetic, thermal and electrochemical studies. Cryomagnetic investigations (77–296 K) reveal a strong antiferromagnetic spin-exchange between the copper(II) ions (J based on H = −2JS1. S2 is 305 cm−1). An electrochemical study of the copper(II) complex shows two distinct quasi-reversible redox peaks (E11/2 = −0.4 and E21/2 = −0.69 V vs saturated calomel electrode), indicating a stepwise reduction of the copper centers (CuIICuII → CuIICuI and CuIICuI → CuICuI). The EPR spectrum is typical of a “rhombic compressed local molecular environment”. The ligand and its copper and zinc complexes exhibit fluorescence at room temperature in DMF. All of the compounds under study were screened for antimicrobial ac...

2,6-Diformyl-p-cresol serves as a starting point for the generation of multidentate N/O/S chelating agents. Condensation with 4-(X-phenyl) thiosemicarbazide yields the pentadentate ligand having SNONS donor sequences, capable of holding two metal ions in close proximity. The ligands behave as mono/di/tri basic depending on the pH of the medium. Stereochemical diversity in the reaction product of such ligands with nickel(II) chloride at different pH is observed. Sterically demanding substituted ligands in association with various exogenous bridges dictate the geometry and coordination number of such complexes. The compounds were investigated by elemental analysis, molar conductivities, electronic spectra, IR, NMR, FAB mass spectra, TG-DTG, magnetic susceptibility measurements. Varieties of geometries such as square planar, square pyramidal, octahedral and square planar–square pyramidal are observed. Cryomagnetic data for the complexes (79–296 K) can be reproduced by an equation based on the Heisenberg model (H=−2JS1S2, S1=S2=1). The singlet–triplet splitting, J varies systematically with the coordination geometry about the Ni2(SNONS) core, with the hydroxo bridged complex exhibiting the greatest degree of antiferromagnetic coupling. The coupling is somewhat weaker for the chloro-bridged complexes. None of the complexes have shown any appreciable antimicrobial activity.

A new binucleating ligand containing phenoxide as an endogenous bridging group, 2,6-diformyl-p-cresol bis(2-furanthiocarboxyhydrazone) and its binuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes with chloride ion as an exogenous bridge, have been obtained. The complexes were characterized by elemental analysis, molar conductivities, magnetic moment measurements at room temperature, electronic, IR, 1H-NMR, EPR, FAB spectral studies and thermal data. The copper complex assumes a tetranuclear structure composed of two binuclear units related by a center of symmetry. The dimeric nature of copper(II) complex is supported by FAB. This complex is EPR silent. Room temperature magnetic moment reveals the operation of a significant antiferromagnetic spin exchange between the metal centers. Ligand and its copper and zinc complexes exhibit fluorescence at room temperature in DMF. All the compounds show an appreciable antimicrobial activity.

New dinuclear complexes of macrocycles/macroacycles/oximeshaving a reactive peripheral thioketo functional group were synthesized using2,6-diformyl-p-cresol as parent compound and thiocarbohydrazide/variousdiamines as side arms. Thioenolization and subsequent coordination to metal ionof the thio-keto sulfur is observed in asymmetric macrocycles and oxime complexes,while it is kept away from the coordination sphere in symmetric macrocycles. Magnetic susceptibility measurements over the range 7–300 K confirm that the copper(II) centersof the symmetric and asymmetric macrocycles are antiferromagnetically coupled, withvalues for the exchange coupling constant J through the phenolate oxygens of -610 to-580 cm-1, respectively. The ligands and their complexes are found to be excellent fungistatic agents.

Four binuclear transition metal(II) complexes: [Co2L(μ-Cl)Cl2] · 2H2O, [Ni2L(μ-Cl)Cl2(H2O)2] · 2H2O, [Cu2L(μ-Cl)Cl2] · 2H2O and [Zn2L(μ-Cl)Cl2] · 2H2O, where LH is the binucleating ligand 2,6-diformyl-4-methylphenol bis(2-hydrazino benzothiazole), were prepared. Based on the i.r. spectra, elemental analysis, conductivity measurements and thermal analysis, we propose that these complexes contain an endogenous phenoxide bridge and an exogenous chloride bridge. Magnetic and spectral data supports the existence of a weak antiferromagnetic interaction between the metal ions, and octahedral for NiII and a square pyramidal environment for remaining complexes. The compounds show significant growth inhibitory activity against the fungi, Aspergillus niger and Candida albicans, as compared to antibacterial activity against Bacillus cirroflagellosus and Pseudomonas auregenosa.

Oxovanadium (IV) complexes, [(VO)2L′(acac)] (where L′H3=thiosemicarbazones derived from 2,6-diformyl-p-cresol with thiosemicarbazides) have been synthesised and characterised using physico-chemical techniques. The complexes have a stoichiometry of 2:1 (M/L) wherein phenolic oxygen is coordinated to two metal atoms to form M–O–M bridge. Each metal atom exhibits a coordination number of five. The transition energies ΔE1 and ΔE2 obtained from the electronic absorption spectra of the VO2+-complex in conjunction with the spin-Hamiltonian parameters obtained from EPR data are used to evaluate the spin-orbit coupling constant, the dipolar and the Fermi-contact terms. The bonding coefficients α2 and β2 are evaluated from the available molecular-orbital theories and the experimental data. The various terms evaluated are correlated and the general behaviour of the VO2+ ion in various ligand fields is discussed.

A novel dinucleating pentadentate Schiff base, resulting from the condensation of 2,6-diformyl-p-cresol and N-methyl-indolyl-3-thiohydrazide, and its Zn complex have been prepared and characterized on the basis of elemental analysis, IR, UV-Visible,1H NMR and13C NMR studies. The ligand is acyclic and consists of a phenolate head unit, with two inbuilt azomethine shoulders and two indole thiohydrazide arms forming SNONS coordinating sites. NMR and IR spectral studies show that the ligand exists in thioketo form. Each Zn ion in the dinuclear core is in tetrahedral environment with endogenous phenolate bridging and exogenous acetate bridging. The zinc complex in DMF exhibits fluorescence.

With the aim to design addressable magnetically-active carbon nanotubes (CNTs) for cancer treatment, the use of Fe-filled CNTs (Fe@MWCNTs) as multifunctional scaffolds is reported for exohedrally anchoring a monoclonal antibody (mAb) known to bind a plasma membrane receptor over-expressed in several cancer cells (EGFR). Comprehensive microscopic (transmission electron microscopy, atomic force microscopy, and scanning electron microscopy) and spectroscopic (Raman, Fe Mossbauer, energy dispersive spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction) characterizations reveal the efficient confinement of magnetically-active Fe phases (α-Fe and FeC), while compositional evaluations through XPS, thermogravimetric analysis and gel electrophoresis confirm that mAb immobilization onto Fe@MWCNTs occurs. Enzyme-linked immunosorbent assay (ELISA), confocal microscopy imaging and western blotting confirm the targeting action toward EGFR-overexpressing cell lines (EGFR+). In vitro magnetic filtration experiments demonstrate that a selective removal of EGFR+ cells from a mixed population of healthy cell lines could be obtained in very short times (≈10 min). Cytotoxicity evaluations by classic cell staining procedures after application of an electromagnetic radiation inducing magnetic fluid hyperthermia (MFH), show a selective suppression of the EGFR+ cell line. Molecular dynamics and docking simulations of the hybrid mAb/Fe@MWCNTs conjugates nicely show how the presence of the CNT framework does not sterically affect the conformational properties of the two antigen binding regions, further supporting the biochemical findings. Encapsulation of Fe phases inside multiwalled carbon nanotubes (MWCNTs) allows isolating reactive magnetic phases exerting magnetic fluid hyperthermia responses. In particular, bioconjugation of Fe@MWCNTs with monoclonal antibody Cetuximab enables the selective in vitro cancer cell sorting and stimuli-induced cytotoxicity under application of external magnetic inputs. Molecular dynamics calculations shed further light on binding modes and conformational properties of the Ab moieties linked on to the tubular carbon framework.