Polymorphism in metal complexes of thiazole-4-carboxylic acid

Five new molecular complexes of chemical formula [M(4-tza)₂(H₂O)₂] (M = Co, Ni, and Cu) and a complex of [Cu(4-tza)₂]∙4H₂O using thiazole-4-carboxylic acid (4-tza) as the ligand have been successfully synthesized and structurally characterized by single crystal X-ray diffraction. Two district polymorphs (α and β) are found for both [Co(4-tza)₂(H₂O)₂] and [Ni(4-tza)₂(H₂O)₂]. The effects of solvent composition and temperature on the formation of these polymorphs have been investigated and phase behaviour of the polymorphs was studied through X-ray powder diffraction. Unlike two complexes of Co and Ni, [Cu(4-tza)₂(H₂O)₂] does not display polymorphism but exhibits irreversible structural transformation from [Cu(4-tza)₂(H₂O)₂] to the dehydrated form, [Cu(4-tza)₂], upon heating

Molybdenum (VI) imido complexes derived from chelating phenols : Synthesis, characterization and ɛ-Caprolactone ROP capability

Reaction of the bulky bi-phenols 2,2′-RCH[4,6-(t-Bu)₂C₆H₂OH]₂ (R = Me L¹ᵐᵉH₂, Ph L¹ᵖʰH₂) with the bis(imido) molybdenum(VI) tert-butoxides [Mo(NR¹)(NR²)(Ot-Bu)₂] (R¹ = R² = 2,6-C₆H₃-i-Pr₂; R¹ = t-Bu, R² = C₆F₅) afforded, following the successive removal of tert-butanol, the complexes [Mo(NC₆H₃ᵢ-Pr₂-2,6)₂L¹ᵐᵉ] (1), [Mo(NC₆H₃i-Pr₂-2,6)₂L¹ᵖʰ] (2) and [Mo(Nt-Bu)(μ-NC₆F₅)(L¹ᵐᵉ)]₂ (3). Similar use of the tri-phenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-methylphenol (L²H₃) with [Mo(NC₆H₃ᵢ-Pr₂-2,6)₂(Ot-Bu)₂] afforded the oxo-bridged product [Mo(NC₆H₃i-Pr₂-2,6)(NCMe)(μ-O)L2H]₂ (4), whilst use of the tetra-phenols α,α,α′,α′-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p- or -m-xylene L³ᵖH₄/L³ᵐH₄ led to {[Mo(NC₆H₃ᵢ-Pr₂-2,6)₂]₂(μ-L³ᵖ)} (5) or {[Mo(NC₆H₃ᵢ-Pr₂-2,6)₂]₂(μ-L³ᵐ)} (6), respectively. Similar use of [Mo(NC₆F₅)₂(Ot-Bu)₂] with L³ᵖH₄ afforded, after work-up, the complex {[Mo(NC₆F₅)(Ot-Bu)₂]₂(μ-L³ᵖ)}·6MeCN (7·6MeCN). Molecular structures of 1, 2·CH₂Cl₂, 3, 4·6MeCN, 6·2C₆H₁₄, and 7·6MeCN are reported and these complexes have been screened for their ability to ring open polymerize (ROP) ε-caprolactone; for comparative studies the precursor complex [Mo(NC₆H₃ᵢ-Pr₂-2,6)₂Cl₂(DME)] (DME = 1,2-dimethoxyethane) has also been screened. Results revealed that good activity is only achievable at temperatures of ≥100 °C over periods of 1 h or more. Polymer polydispersities were narrow, but observed molecular weights (Mn) were much lower than calculated values

(1-Butyl-1,4-diazabicyclo[2.2.2]octon-1-ium-κN4)trichloridocobalt(II)

The title compound, [Co(C 10 H 21 N 2 )Cl3], was obtained as the by-product of the attempted synthesis of a cobalt sulfate framework using 1,4-diaza-bicyclo-[2.2.2] octane as an organic template. The asymmetric unit comprises two distinct mol-ecules, and in each, the cobalt(II) ions are tetra-hedrally coordinated by three chloride anions and one 1-butyl-diaza-bicyclo-[2.2.2]octan-1-ium cation. The organic ligands are generated in situ, and exhibit two forms differentiated by the eclipsed and staggered conformations of the butyl groups. These mol-ecules inter-act by way of C - H⋯Cl hydrogen bonds, forming a three-dimensional hydrogen-bonding array

Microwave-assisted hydrothermal synthesis of carbon monolith via a soft-template method using resorcinol and formaldehyde as carbon precursor and pluronic F127 as template

A new microwave-assisted hydrothermal synthesis of carbon monolith is reported in this work. The process uses microwave heating at 100 °C under acidic condition by employing a triblock copolymer F127 as the template, and resorcinol–formaldehyde as the carbon precursor. Scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen sorption measurements, transmission electron microscopy, X-ray studies and thermogravimetic analysis were used to characterize the synthesized material. The carbon monolith is crack-free, mesoporous and has a high surface area of 697 m²/g. The results demonstrate that the microwave-assisted hydrothermal synthesis is a fast and simple approach to obtain carbon monoliths, as it reduces effectively the synthesis time from hours to a few minutes which could be an advantage in the large scale production of the material

Crystal structures of N ′-Aminopyridine-2-carboximidamide and N ′-{[1-(pyridin-2-yl)ethylidene]amino}pyridine-2-carboximidamide

© Eya'ane Meva et al. 2017. The crystal structures of N,-Aminopyridine-2-carboximidamide (C 6 H 8 N 4 ), 1, and N,-{[1-(pyridin-2-yl)ethylidene]amino}pyridine-2-carboximidamide (C 13 H 13 N 5 ), 2, are described. The non-H atoms in compound 1 are nearly planar (r.m.s. deviation from planarity = 0.0108 Å ), while 2 is twisted about the central N-N bond by 17.8 (2)-. Both molecules are linked by intermolecular N-H·N hydrogen-bonding interactions; 1 forms a two-dimensional hydrogen-bonding network and for 2 the network is a one-dimensional chain. The bond lengths of these molecules are similar to those in other literature reports of azine and diimine systems

Understanding the root causes of natural disasters

Every year disasters take lives, cause significant damage, inhibit development and contribute to conflict and forced migration. Unfortunately, the trend is an upward one. In May 2017, policy-makers and disaster management experts from over 180 countries gathered in Cancun, Mexico, to discuss ways to counter this trend. In the middle of the Cancun summit, news arrived that large parts of Sri Lanka were devastated by floods and landslides, killing at least 150 and displacing almost half a million people. Email Twitter68 Facebook52 LinkedIn21 Print Every year disasters take lives, cause significant damage, inhibit development and contribute to conflict and forced migration. Unfortunately, the trend is an upward one. In May 2017, policy-makers and disaster management experts from over 180 countries gathered in Cancun, Mexico, to discuss ways to counter this trend. In the middle of the Cancun summit, news arrived that large parts of Sri Lanka were devastated by floods and landslides, killing at least 150 and displacing almost half a million people. It was a stark reminder of the summit participants\u27 challenging task of paving the way towards reducing disaster losses significantly by the year 2030 based on the Sendai Framework for Disaster Risk Reduction (DRR). Adopted in 2015, the Sendai Framework outlines seven targets and four priorities for action to prevent new, and reduce existing, disaster risks to economic, physical, social, cultural, health or environmental assets and lives of persons, businesses, communities and countries. Since then, in China, a village in the Sichuan province has been devastated by a landslide and rescuers are still looking for missing people

Crystal structure of 4-carbamoylpyridinium chloride

The hydro­chloride salt of isonicotinamide, C6H7N2O+·Cl-, has been synthesized from a dilute solution of hydro­chloric acid in aceto­nitrile. The compound displays monoclinic symmetry (space group C2/c) at 150 K, similar to the related hydro­chloride salt of nicotinamide. The asymmetric unit contains one protonated isonicotinamide mol­ecule and a chloride anion. An array of hydrogen-bonding inter­actions, including a peculiar bifurcated pyridinium-chloride inter­action, results in linear chains running almost perpendicularly in the [150] and [1-50] directions within the structure. A description of the hydrogen-bonding network and comparison with similar compounds are presented

Polymorphism and solid−gas/solid−solid reactions of isonicotinic acid, isonicotinamide, and nicotinamide copper chloride compounds

The crystal structures of eight new copper chloride coordination complexes with substituted pyridines have been determined through a combination of single crystal X-ray diffraction and ab initio structure solution from X-ray powder diffraction data. The polymeric compounds [CuCl₂(INAc)₂]n (1), [CuCl₂(INAm)₂]n (2), and [CuCl₂(NAm)₂]n (3) (INAc = isonicotinic acid; INAm = isonicotinamide; NAm = nicotinamide) consist of chains of CuCl4 edge-sharing rhombi decorated by the pyridine-based ligands. All three compounds display similar hydrogen bonding interactions but differ in the arrangement of the polymeric chains. 1, 2, and 3 react reversibly with hydrochloric acid in solution/vapor form to produce the corresponding tetrachlorocuprate salts [CuCl₄](H-INAc)₂(H₂O) (4a), [CuCl₄](H-INAc)₂ (4b), [CuCl₄](H-INAm)₂ (form I/form II 5a/5b), and [CuCl₄](H-NAm)₂ (form I/form II 6a/6b). 4a exhibits discrete square planar [CuCl4]₂– ions, whereas the Cu in 4b, 5a, and 5b is in a 4 + 2 coordination. All four compounds display hydrogen bonding arrangements similar to those found in 1 and 2. 6a and 6b differ substantially from these compounds in both the hydrogen bonding contacts and the coordination geometry of the cuprate ion (flattened tetrahedral), though they differ from each other only in the orientation of the amide groups and packing arrangements. The formation of 6a/6b depends on the configuration of nicotinamide in the starting material

Multimetallic lithium complexes derived from the acids Ph₂C(X)CO₂H (X = OH, NH₂) : synthesis, structure and ring opening polymerization of lactides and lactones

Reaction of LiOR (R=t-Bu, Ph) with the acids 2,2/-Ph₂C(X)(CO₂H), X=OH (benzH), NH₂ (dpgH) was investigated. For benzH, one equivalent LiOt-Bu in THF afforded [Li(benz)]2⋅2THF (1⋅2THF), which adopts a 1D chain structure. If acetonitrile is used (mild conditions), another polymorph of 1 is isolated; LiOPh also led to 1. Robust work-up afforded [Li₇(benz)₇(MeCN)] 2MeCN THF (2⋅2MeCN⋅THF). Use of LiOt-Bu (2 equivalents) led to {Li₈(Ot-Bu)₂[(benz)](OCPh₂CO₂CPh₂CO2t-Bu)₂(THF)₄} (3), the core of which comprises two open cubes linked by benz ligands. For dpgH, two equivalents of LiOt-Bu in THF afforded [Li6(Ot-Bu)₂(dpg)₂(THF)₂] (4), which contains an Li₂Ov 6-step ladder. Similar reaction of LiOPh afforded [Li₈(PhO)₄(dpg)₄(MeCN)₄] (5). Complexes 1–5 were screened for their potential as catalysts for ring opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL), rac-lactide (rac-LA) and δ-valerolactone (δ-VL). For ROP of ϵ-CL, conversions > 70 % were achievable at 110 °C with good control. For rac-LA and δ-VL, temperatures of at least 110 °C over 12 h were necessary for activity (conversions > 60 %). Systems employing 2 were inactiv

Turning on ROP activity in a bimetallic Co/Zn complex supported by a [2+2] Schiff-base macrocycle

Homo-dinuclear Co and Zn complexes derived from the macrocycle LH2, {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2 (R = Me, tBu), revealed near inactivity for the ring opening polymerization (ROP) of the cyclic esters δ-valerolactone (δ-VL) and ϵ-caprolactone (ϵ-CL). By contrast, the hetero-bimetallic complexes [LCo(NCMe)(μ-Br)ZnBr]·nMeCN (n = 3 or 3.25) were found to be efficient catalysts for the ROP of ϵ-CL and δ-VL