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An illustrious complex [Fe(ptz)](BF) (ptz = 1-propyl-tetrazole) ( 1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by Fe 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 [Fe(HO)](BF) salt on this membrane. [ABSTRACT FROM AUTHOR]

A series of novel 3-{[(5-phenyl-1,3,4-thiadiazol-2-yl)imino] methyl}quinoline-2-thione (2a-c) and 2-phenyl-3-pyrido[3,2][1,3,4]thiadiazolo[3,2]quinoline derivatives (3a-c) were prepared by a facile synthetic method using an anhydrous potassium carbonate catalyst. The newly synthesized heterocyles were characterized by elemental analysis, FT-IR, 1H-NMR, and mass spectral data. The selected compounds were studied for interaction with calf thymus-DNA(CT-DNA) by electronic spectra and viscosity measurements, as well as thermal denaturation studies. Upon binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. The binding constant (Kb) observed value of 8.4 × 105 M-1 for (2a) and 8.2 × 105 M-1 for (3a) suggested that compound (2a) binds more avidly to CT-DNA than compound (3a). The increasing viscosity of sonicated rod-like DNA fragments and the melting temperature of DNA, in the presence of compound solutions, support the binding mode. The synthesized derivatives have been screened for antibacterial and antifungal activities. [ABSTRACT FROM AUTHOR]

A facile one-step procedure for the preparation of 4,4'-bis-1,2,4-triazole is reported. Direct transamination of N,N-dimethyl?formamide 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. [ABSTRACT FROM AUTHOR]

A mononuclear iron(II) neutral complex (1) is screened for sensing abilities for a wide spectrum of chemicals and to evaluate the response function toward physical perturbation like temperature and mechanical stress. Interestingly, 1 precisely detects methanol among an alcohol series. The sensing process is visually detectable, fatigue-resistant, highly selective, and reusable. The sensing ability is attributed to molecular sieving and subsequent spin-state change of iron centers, after a crystal-to-crystal transformation. [ABSTRACT FROM AUTHOR]

Objective: External jugular vein (EJV) aneurysm is an extremely uncommon clinical condition. We have studied the clinical profile and need for surgery in this present seven case series of primary external jugular vein aneurysms. Method: Over the past three years, we have diagnosed and managed aneurysms of external jugular vein in seven patients, who presented with swelling in the posterior triangle of the neck. Venous duplex was obtained in all the patients, followed by computed tomography (CT) in three patients and one patient reported with magnetic resonance (MR) venography from another hospital. Three patients had symptoms ranging from mild intermittent discomfort to moderate pain underwent excision of aneurysm after ligation of both ends of EJV. Four patients had swelling on the lateral side of the neck due to EJV aneurysm, with no other associated symptoms. They were kept on six monthly follow-ups. Result: We operated three patients, as they were symptomatic, of which only two had thrombus in the aneurysmal sac. All three symptomatic patients had aneurysm of size >5 cm. Post-surgery and on subsequent follow-ups they were asymptomatic. The four asymptomatic patients kept on conservative management did not develop any thrombosis of aneurysm sac in follow up. Conclusion: Surgical excision is indicated for symptomatic patients with EJV aneurysm, preferably for size > 5 cm because of their higher association with thrombosis or symptoms. Asymptomatic patients can be managed non-operatively with regular surveillance by clinical examination and venous duplex or can be treated if patients insist due to cosmetic reasons. [ABSTRACT FROM AUTHOR]

By limiting the heat spread during a fire hazard, intumescent coatings are important components of passive protection systems. They swell due to heat induced reactions of micro constituents and are transformed into carbonaceous porous-like media, known as intumescent chars. Their multiscale inner structures, key elements of performance, are costly to predict by recurrent and large scale fire testing while numerical simulations are challenging due to complex kinetics. Hence, we propose a novel approach using the fractal theory and the random nature of events to conceptualize the coating expansion. Experimental specimens were obtained from fire protective coatings exposed to bench scale hydrocarbon fire. Mass fractals were evidenced in the slices of 3D sample volumes reconstructed from X-ray microtomography. Consequently, geometrical building blocks were simulated by random walk, active walk, aggregation-like and site percolation: physical-chemical modes of action were inherent in the attribution of the randomness. It is a first demonstration to conceptualize different types of intumescent actions by a generalized approach with dimensionless parameters at multiscale, thus eliminating the simulation of complex kinetics to obtain a realistic morphology. Also, fractal results brought new evidence to former chemical analyses on fire test residues trying to explain the kinetics of expansion. Expected outcomes are to predict virtually the reaction of fire protective systems hence to speed-up the assessment of fire performance through computed properties of virtual volumes. [ABSTRACT FROM AUTHOR]

The effect of electronegativity (F and Cl atom) on structural, spectrophotometric, thermo-chemical properties, and solvent effect on electronic absorption spectra of {3-(3,5-dichloro-2-hydroxyphenyl)-5-[(4-fluorophenyl)amino] isoxazol-4-yl}(phenyl)methanone (Ia) and {3-(3,5-dichloro-2-hydroxyphenyl)-5-[(4-chlorophenyl)amino] isoxazol-4-yl}(phenyl) methanone (Ib) were studied by DFT method using PBE1PBE functional with 6-311++g (d, p) basis set. The results show that the electronegativity of halogen group affect the bond length, atomic charges, excited wavelength, molecular orbital energy gap, vibration frequency, thermo-chemical parameters, and stability of compounds. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A conformationally flexible triazole-carboxylic acid ligand derived from an L-amino acid, namely, 4H-1,2,4-triazol-4-yl-acetic acid (aHGlytrz), 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. [ABSTRACT FROM AUTHOR]

The spin crossover behaviour of a new class of Fe coordination polymers [Fe(phtptrz)]I ( 1), [Fe(phtptrz)](ReO)•CHOH ( 2) and [Fe(phtptrz)]TaF•6HO ( 3) based on a novel ligand 4-(3 -N-phtalimido-propyl)-1,2,4-triazole (phtptrz), were investigated by temperature dependent Fe Mössbauer 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 T ~ 163 K and 137 K, respectively. A spin state crossover is also identified for 3. [ABSTRACT FROM AUTHOR]

A new 1D coordination polymer [Fe(βAlatrz)](ClO) ∙ HO (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 Fe Mössbauer spectroscopy. The temperature dependence of the high-spin molar fraction derived from Fe Mössbauer spectroscopy recorded on cooling below room temperature reveals a gradual single step transition with T = 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 T matching the one determined by both SQUID and Fe Mössbauer 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. [ABSTRACT FROM AUTHOR]

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 Mssbauer 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) Å, b = 9.72(1) Å, c = 6.361(9) Å at 298 K (low-spin state) and a = 14.37(2) Å, b = 9.61(4) Å, c = 6.76(4) Å 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 interaction parameter of J = 496 K. The crystal structure of [Cu(NH2trz)3](NO3)2·H2O (2) was obtained thanks to high quality single crystals prepared by slow evaporation after hydrothermal pretreatment. The catena poly[μ-tris(4-amino-1,2,4-triazole-N1,N2) copper(II)] dinitrate monohydrate (2) crystallizes in the monoclinic space group C2/c, with a = 16.635(6) Å, b = 13.223(4) Å, c = 7.805(3) Å, β = 102.56(3)°, Z = 4. Complex 2 is a 1D infinite chain containing triple N1,N2-1,2,4-triazole bridges with an intra-chain distance of Cu⋯Cu = 3.903(1) Å. A dense H-bonding network with the nitrate counteranion involved in intra-chain and inter-chain interactions is observed. Such a supramolecular network could be at the origin of the unusually large hysteresis loop displayed by 1 (ΔT ∼ 33 K), as a result of an efficient propagation of elastic interactions through the network. This hypothesis is strengthened by the crystal structure of 2 and by the absence of crystallographic phase transition for 1 over the whole temperature range of investigation as shown by XRPD. [ABSTRACT FROM AUTHOR]

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)ClO 4 ] ( 1 ), [Cu(phen)(gly)]ClO 4 ( 2 ) and [Cu(L 1 ) 2 (H 2 O) 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-4 H -1,2,4-triazol-4-amine (H 1 L 1 ). 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, H 2 O 2 . All the three complexes have primarily shown the DNA cleaving activity. [ABSTRACT FROM AUTHOR]

Abstract: 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 (5–293K) and pressure range (1bar–12kbar) by magnetic susceptibility measurements and variable temperature 57Fe Mössbauer 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. [Copyright &y& Elsevier]

Introduction: Mucinous cystic neoplasms (MCN) are mucin-producing epithelial cell tumors of pancreas. They consist of an ovarian-type stroma expressing estrogen and progesterone receptors. Pregnancy-associated MCNs are presumed to be larger in size and more aggressive without any concrete evidence., Objective: and Data Sources: Systematic review of published literature using PubMed and Google Scholar databases. Original articles including case reports and series published between 1970&2021 were included wherein MCN was diagnosed during pregnancy/within one-year post-partum. Thirty-three publications having 36 cases, adding one of our own patient were analyzed in this review., Result: Median age at presentation was 32 years. Only three (9%) patients were asymptomatic. Mean size of MCN was 135 mm. Ten patients (27%) reported an increase in size during pregnancy. Most tumors involved body and tail of pancreas (60%). Distal pancreatectomy with splenectomy was the most common resection performed (57%). No foetal mortality was reported to date., Conclusion: Pregnancy may cause a rapid increase in size of MCN. Decision-making is more complex and needs a fine balance between optimal oncological and obstetric outcomes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Surgical site infection continues to be a major problem after laparotomy for perforation peritonitis, as it increases morbidity and hospital stay and decreases the quality of life. Intra-abdominal drain placement is a routine practice in perforation peri-tonitis. The aim of our study is to compare the incidence of surgical site infection in two groups of patients who were operated for perforation peritonitis: The first group received the intraperitoneal drain, while no drain was placed in the second group., Methods: The present single-center, prospective, non-randomized study was conducted in the Department of General Surgery at the Postgraduate Institute of Medical Education and Research, India. A total of 122 patients underwent exploratory laparotomy for gastroduodenal and small bowel perforation peritonitis, of which 100 participants were included in this study, based on specified cri-teria for inclusion and exclusion. A total of 50 participants each were included in the drain group and the no drain group, respectively. A drain was placed in every alternate patient with perforation peritonitis who received primary closure or resection anastomosis. Patients with diabetes, renal failure, and hemodynamic instability and those who presented more than 72 h since symptom onset were excluded from the study. Peritoneal fluids were cultured. The primary endpoint was to identify the incidence of surgical site infections (SSIs) in the two groups. We also compared the time taken for the return of bowel movements, duration for which a nasogastric tube was inserted, whether any intervention was performed under local or general anesthesia within 30 days of surgery, the duration of hospital stay, and the ease of diagnosing repair leak in the post-operative period in both the groups., Results: Demographics of participants in both the groups were matched. No significant difference was observed between the drain and no-drain groups with respect to the incidence of surgical site infection (p=0.779). The duration of surgery and length of hospital stay were significantly lower in the no drain group. A significant difference was observed between the two groups concerning the peritoneal culture growth, and increased bacterial growth was seen in the drain group. No significant difference in morbidity was noted between the two groups, which was classified according to the Clavien-Dindo classification., Conclusion: Routine use of intra-abdominal drains was not found to be effective in preventing SSIs, but a selection bias cannot be ruled out. Patients with no drains had a significantly shorter duration of hospital stay.

Introduction Abdominal aortic aneurysms (AAA) are uncommon in young adults ≤55 years of age. There is a lack of literature on clinical characteristics, risk factors, and therapeutic outcomes so we present a case series of 11 patients of AAA aged ≤55 years. Methods We included single-center retrospective case series between 2013 to 2020. We reviewed 44 patients who were operated for AAA in a tertiary care center in India. We identified 13 patients who were ≤55 years; two patients with incomplete records were excluded. A patient information sheet was used to retrieve demographic data, clinical presentation, outcomes, and follow-up. Results Out of 11 patients, 10 were men. Nine patients (81.8%) had symptomatic AAA. The majority (45.4%) exhibited an infrarenal aneurysm and the median size of the aneurysm was 5.8 cm (IQR: 5.5-6.4 cm). Eight patients (72.7%) had a history of smoking. Hypertension was observed in six patients and one patient had associated coronary artery disease. Clamping time was > 45 minutes among three patients; all smokers. Blood loss was > 500 ml in five patients. The median length of hospital stay was 10 days (7-40); more among patients with metabolic equivalents (METS) score < 4, 14.5 (8-19) days. No grade III-IV complications and mortality were noted with a median follow-up of 15 months, with all patients living. Conclusion The aneurysm was symptomatic in the majority of participants. An association of smoking in increasing both the median clamping time and length of hospital stay was seen. No mortality and good disease-free follow-up suggested good outcomes., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Behera et al.)

A 45-year-old woman with known hypothyroidism and no other comorbidities was incidentally found to have multiple right renal artery aneurysms. The largest aneurysm measured 5 x 4.5 cm and arose from an inferior segmental branch while two smaller aneurysms arose from an upper segmental branch of the right renal artery. We performed an ex-vivo repair with reverse saphenous vein graft under cold preservation followed by orthotopic kidney auto-transplantation. Her postoperative course was unremarkable and at 1-year follow-up her right kidney is preserved. In this article, we report successful treatment of complex multiple right renal artery aneurysms and describe the surgical technique used for successful repair., Competing Interests: Conflicts of interest: No conflicts of interest declared concerning the publication of this article., (Copyright© 2021 The authors.)

A 49-year-old woman presented to surgery outpatient clinic with the awareness of a right lower abdomen asymptomatic lump for one week. Contrast-enhanced CT of the abdomen demonstrated a 10×11×15 cm heterogeneous lesion anterior to the ileocecal junction with the possibility of leiomyosarcoma. The patient was prepared for laparotomy and intraoperative there was a large tumour arising from the medial wall of cecum. Right haemicolectomy was performed, and histopathology came as a desmoid tumour of the cecum. The patient had an uneventful postoperative course and is well on 1-year follow-up., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Introduction: Haemangiomas are the most common benign tumours of the liver. Most of them are asymptomatic. Giant hepatic haemangioma is defined as size greater than 5 cm in diameter. The surgical treatment for giant hepatic haemangioma is not very well defined and reported. Here we analysed the treatment outcome of giant hepatic haemangiomas and redefined the nomenclature according to the size and proposing an algorithm for management of all hepatic haemangiomas., Material and Methods: Retrospective analyses of 6 giant hepatic haemangioma more than 10 cm in size treated by a single surgeon were included. The clinical characteristics, diagnosis, managements and outcomes were recorded. Review of literature was done for definitions, management strategies and outcome of giant haemangiomas and an algorithm was proposed., Results: Five patients were female and the mean age was 36.6 years (range 32 to 45). Pain abdomen was the most common symptoms (100%). Ultrasound abdomen was the initial diagnostic modality followed by contrast enhanced computed tomography. The mean size of haemangioma was 17.4cm (range 12cm to 32cm). Four patients had haemangioma in the left lobe and two had in the right lobe of liver. Formal hepatectomy was done in three patients and enucleation was done in three patients. The mean operating time was 3.66 hours (range 2.5 hours to 5 hours). The mean blood loss was 840ml (range 300ml to 1500ml). There was no surgical morbidity or mortality. On follow-up no haemangioma related complications are reported., Conclusions: Giant hepatic haemangioma is mostly symptomatic. Hepatectomy and enucleation can be done without significant morbidity and mortality. There is a need for redefining the nomenclature of giant hepatic haemangiomas according to the size.

A 21-year-old unmarried and primigravida female indulged in criminal abortion at 18 weeks of gestation with the help of a village midwife. Instrumentation was done, and it led to uterine perforation with prolapse of 200 cm of small bowel through vagina. She was managed with resection of 160 cm of necrotic small bowel, repair of the uterine defect, and end jejunostomy, which was anastomosed with distal ileum three months later. This case highlights the risks of illegal abortion and the primitive societal mindset that forces unmarried women to resort to such means., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2020, Singla et al.)

The contribution of copper complexes of salen-based Schiff bases N, N'-bis(salicylidene)ethylenediamine (C1), N, N'-bis(4-hydroxysalicylidene)ethylenediamine (C2), and N, N'-bis(5-hydroxysalicylidene)ethylenediamine (C3) to the flame retardancy of thermoplastic polyurethane (TPU) is investigated in the context of minimizing the inherent flammability of TPU. Thermal and fire properties of TPU are evaluated. It is observed that fire performances vary depending upon the substitution of the salen framework. Cone calorimetry [mass loss calorimetry (MLC)] results show that, in TPU at 10 wt % loading, C2 and C3 reduce the peak of heat release rate by 46 and 50%, respectively. At high temperature, these copper complexes undergo polycondensation leading to resorcinol-type resin in the condensed phase and thus acting as intumescence reinforcing agents. C3 in TPU is particularly interesting because it delays significantly the time to ignition (MLC experiment). In addition, pyrolysis combustion flow calorimetry shows reduction in the heat release rate curve, suggesting its involvement in gas-phase action. Structural changes of copper complexes and radical formation during thermal treatment as well as their influence on fire retardancy of TPU in the condensed phase are investigated by spectroscopic studies supported by microscopic and powder diffraction studies. Electron paramagnetic resonance (EPR) spectroscopy was fully used to follow the redox changes of Cu(II) ions as well as radical formation of copper complexes/TPU formulations in their degradation pathways. Pulsed EPR technique of hyperfine sublevel correlation spectroscopy reveals evolution of the local surrounding of copper and radicals with a strong contribution of nitrogen fragments in the degradation products. Further, the spin state of radicals was investigated by the two-dimensional technique of phase-inverted echo-amplitude detected nutation experiment. Two different radicals were detected, that is, one monocarbon radical and an oxygen biradical. Thus, the EPR study permits to deeply investigate the mode of action of copper salen complexes in TPU.

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.

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 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.