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A series of Hoveyda–Grubbs second-generation catalysts containing N-alkyl/N′-aryl N-heterocyclic carbene (NHC) ligands were synthesized and investigated in representative olefin metathesis reactions. Steric perturbations of unsymmetrical NHCs were achieved through modulation of the hindrance of alkyl (neopentyl, neophyl, cyclohexyl) and aryl (2-isopropylphenyl, mesityl) substituents at the nitrogen atoms in combination with different backbone configurations (synand anti). The NHC substitution patterns strongly influence the stability and reactivity of the corresponding complexes. In general, complexes bearing an antiNHC backbone are more stable and more active than their corresponding synisomers. In both the series, the presence of bulky, highly branched N-alkyl groups tends to give reduced catalytic differences between synand antiisomers, whereas the nature of the N′-aryl substituent (2-isopropylphenyl or mesityl) gives rise to different activity and/or selectivity. Of note, an N′-mesityl catalyst with antibackbone was found to be highly competent in the ethenolysis of ethyl oleate, achieving up to 90% selectivity for the formation of terminal olefins.

[Cu2(μ4-O)Cu2] and [Cu2(μ3-OH)2Cu2] geometrical arrangements are found in a new family of tetranuclear complexes: [Cu4(μ4-O)(μ-bip)2(μ-O2CPh)4]·0.5CH2Cl2(1·0.5CH2Cl2), [Cu4(μ3-OH)2(μ-bip)2(N3)4] (2), and [Cu4(μ3-OH)2(μ-bip)2(NCS)4(DMF)2] (3·2DMF) [Hbip = 2,6-bis(benzyliminomethyl)-4-methylphenol; DMF = dimethylformamide]. These complexes have been characterized by X-ray crystallography, and their magnetic properties have been studied. Complex 1reacts with azide and thiocyanate anions, leading to 2and 3with a change of the [Cu4(μ4-O)] core into [Cu4(μ3-OH)2] units. These compounds are new examples of [Cu4] complexes where CuIIions are connected by two types of water-derived ligands: oxide and hydroxide. Formation of these [Cu4] complexes can be controlled by changing the bridging ligands, which allows an effective tuning of the self-assembly. The study of the magnetic properties reveals that these complexes exhibit strong intramolecular antiferromagnetic interactions to yield a ST= 0 ground state. For the three complexes, the temperature dependence of the magnetic susceptibility was fitted using a model with two isolated S= 1/2 dimers based on the H= −2J{SCu,1·SCu,2} spin Hamiltonian with J/kB= −289 K for 1; J/kB= −464 and −405 K for 2and 3, respectively (where Jis the exchange constant through the oxido−phenoxido or hydroxido−phenoxido bridges, respectively).

The coordination behavior and reactivity of the phenol-substituted bis(pyrazolyl)methane ligands, (3,5-tBu2-2-phenol)bis(3,5-Me2-pyrazol-1-yl)methane (L1-H) and 2-phenol-bis(3,5-Me2-pyrazol-1-yl)methane (L2-H) have been investigated in the metal complexes (L1-H)CoCl2(1), (L1-H)ZnCl2(2), (L3)CuCl2(3), (L2)2Co2Cl2(4) (L2-H)ZnCl2(5), and (L2-H)CuCl2·H2O (6). The mononuclear tetrahedral cobalt complex 1was isolated and fully characterized by X-ray single crystal diffraction and 1H NMR spectroscopy and relaxometry. The neutral L1-H is κ2-coordinated to the metal center whereas the not coordinated hydroxy-phenyl group is involved in extended intermolecular hydrogen bonds. Aerobic oxidation of L1-H was observed in the reaction of this ligand with CuCl2to yield the para-quinone derivative L3(L3= 2-tBu-6-(bis(3,5-Me2-pyrazol-1-yl)methyl)cyclohexa-2,5-diene-1,4-dione). Upon oxidation L3resulted κ2-coordinated to the tetrahedral Cu(II) metal center, affording 3. The reaction of L2-H with CoCl2·6H2O produced the elimination of 1 equiv of hydrochloric acid and the formation of the binuclear complex 4in which one cobalt is in an octahedral environment featuring two κ3-coordinated deprotonated ligands whereas the second cobalt center is detected in tetrahedral coordination geometry, bound to the octahedral cobalt via two phenoxo bridging moieties. Interestingly L2-H, (3-tBu-2-phenol)bis(3,5-Me2-pyrazol-1-yl)methane (L4-H), or (5-tBu-2-phenol)bis(3,5-Me2-pyrazol-1-yl)methane (L5-H) were not oxidized in the reaction with CuCl2. The reaction of the ligand L2-H with ZnCl2and CuCl2·2H2O yielded the κ2-coordinated tetrahedral complex 5and the square planar complex 6, respectively. The application of the cobalt complex 1as molecular dosimeter for H2S was explored and compared to that of the zinc analogue 2. Density functional theory (DFT) calculations and NMR experiments to assess the possible mechanisms of H2S detection by both 1and 2are also described.

A combined experimental and computational study on the solubility and biological activity of carbamazepine (CBZ), three co-crystals (COCs), and their parent physical mixtures (MIXs) is carried out to shed light onto the possible modulation of the drug properties. Two of the considered co-crystals, CBZ with vanillic acid (VAN) and CBZ with 4-nitropyridine N-oxide (NPO), are newly synthesized, while the third, CBZ with succinic acid (SUC), is already known. While COC CBZ-VAN and MIX CBZ-NPO did not alter the CBZ dissolution profile, MIX CBZ-SUC and COCs CBZ-SUC and CBZ-NPO inhibit straightaway its solubility. On the other hand, MIX CBZ-VAN induced a remarkable increase of the drug solubility. Analogously, different CBZ permeability values were registered following its dissolution from MIXs and COCs: CBZ and MIXs CBZ-SUC and CBZ-VAN slightly reduce the integrity of intestinal cell monolayers, whereas MIX CBZ-NPO and COCs CBZ-SUC, CBZ-VAN, and CBZ-NPO maintain the monolayer integrity. The molecular aggregates formed in solution were found to be the key to interpret these different behaviors, opening new possibilities in the pharmaceutical utilization and definition of drug co-crystals.