Rotational Spectroscopy Meets Quantum Chemistry for Analyzing Substituent Effects on Non-Covalent Interactions: The Case of the Trifluoroacetophenone-Water Complex

The most stable isomer of the 1:1 complex formed by 2,2,2-trifluoroacetophenone and water has been characterized by combining rotational spectroscopy in supersonic expansion and state-of-the-art quantum-chemical computations. In the observed isomer, water plays the double role of proton donor and acceptor, thus forming a seven-membered ring with 2,2,2-trifluoroacetophenone. Accurate intermolecular parameters featuring one classical O-H···O hydrogen bond and one weak C-H···O hydrogen bond have been determined by means of a semi-experimental approach for equilibrium structure. Furthermore, insights on the nature of the established non-covalent interactions have been unveiled by means of different bond analyses. The comparison with the analogous complex formed by acetophenone with water points out the remarkable role played by fluorine atoms in tuning non-covalent interactions.

Six-coordinate mononuclear dysprosium(iii) single-molecule magnets with the triphenylphosphine oxide ligand

Three rare octahedral mononuclear DyIII complexes bearing triphenylphosphine oxide and halide ligands are reported. The Cl− and Br− analogues exhibit SMM behavior under a small dc field. Ab initio CASSCF calculations reveal a higher energy barrier for an analogous complex with iodides.

Ionic complex of a rhodamine dye with aggregation-induced emission properties

An AIE-active rhodamine based luminogen was prepared via a complexation reaction between non-emissive rhodamine hydrazide (RdH) and bulky camphorsulfonic acid (CSA). Besides acting to open the spirolactam ring of RdH, CSA also imposes a rotational restriction on the resultant ionic complex, RdH(CSA)x. Without CSA, the analogous complex RdH(HCl)3 is a luminogen with aggregation-caused quenching (ACQ) properties. The ionic bonds of RdH(CSA)3 are sensitive to several external stimuli and therefore it is a luminescent sensor for metal ions, organic amines and the blood protein bovine serum albumin (BSA). Besides being a sensor for BSA, the ionic RdH(CSA)3 is also a denaturant capable of uncoiling the peptide chain of BSA.

Trinuclear nickel coordination complexes of phenanthrene-9,10-dione dioxime

A trinuclear nickel complex of phenanthrene-9,10-dione dioxime (H2pqd), namely bis[μ2-9,10-bis(oxidoimino)phenanthrene]bis[μ2-10-(oxidoimino)phenanthrene-9-one oxime](phenanthrene-9,10-dione dioxime)trinickel(II) toluene disolvate, [Ni3(C14H8N2O2)2(C14H9N2O2)2(C14H10N2O2)]·2C7H8, has been isolated and its crystal structure determined. This complex features three independent NiIIatoms that are arranged in a triangular fashion along with five supporting ligands. There are two square-planar NiIIatoms and a third pseudo-octahedral NiIIatom. While the square-planar NiIIatoms are stacked, there are no ligand bridges between them. Each square-planar NiIIatom, however, bridges with the pseudo-octahedral NiIIatom through Ni—N—O—Ni and Ni—O—Ni bonds. A fluoridoboration reaction of the proton-bridged species gave the analogous complex bis(μ2-bis{[10-(oxidoimino)-9,10-dihydrophenanthren-9-ylidene]amino}difluoridoborato)(phenanthrene-9,10-dione dioxime)trinickel(II) dichloromethane trisolvate, [Ni3(C28H16BF2N4O2)4(C14H10N2O2)]·3CH2Cl2, which shows the same binding structure, but features a widened Ni—Ni interaction between the square-planar NiIIatoms. The proton-bridged complex completes the macrocyclic coordination around the square-planar NiIIatoms by means of an O—H...O hydrogen bond. Both compounds feature O—H...N hydrogen bonds between the oxime and the N atoms attached to square-planar nickel atom. The nickel units show no direct interaction with their nearest neighbors in the extended lattice. Two π-stacking interactions between adjacent molecules are found: one with a centroid–centroid distance of 3.886 (2) Å and the other with a centroid–centroid distance of 4.256 (3) Å. In the latter case, although not aromatic, the distance to the centroid of the central phenanthrene ring is shorter, with a distance of 3.528 (3) Å. Toluene molecules occupy the solvent channels that are oriented along thecaxis. In the fluoridoboronate structure, the solvent (DCM) was too badly disordered to be modelled, so its contribution was removed using SQUEEZE [Spek (2015).Acta Cryst.C71, 9–18].

Responsibility for Another’s Debt: Suretyship, Solidarity, and Imperfect Delegation

Legal evolution is often achieved by taking a fresh look at venerable institutions whose interpretation has become thwarted, constricted, or stale. Presumptions established to protect debtors and sureties at articles 1525 and 2335 of the Civil Code of Québec have prevented jurists from borrowing freely from the rules of solidarity and suretyship. Where one person is undoubtedly responsible for the debt of another, even in the absence of a suretyship agreement, the author argues it should be possible to apply the law of suretyship by analogy. Where two persons are each liable to perform the same obligation in full, it is likewise appropriate to apply the rules of solidarity. The author’s analysis proceeds in three parts: an introduction of the basic structure of suretyship and solidarity (Part I), a discussion of important differences in the law of suretyship and solidarity (Part II), and an argument that the solidarity and suretyship models should be used to illuminate analogous complex relations where multiple persons are responsible for the same debt (Part III). More specifically, in the situation of imperfect delegation, where a person assumes liability to a creditor for payment of a debt owed by another, but the original debtor is not discharged and remains liable in case of non-payment by the new debtor, it is appropriate to apply by analogy the law of suretyship.

Sarcospan reduces dystrophic pathology: stabilization of the utrophin–glycoprotein complex

Mutations in the dystrophin gene cause Duchenne muscular dystrophy and result in the loss of dystrophin and the entire dystrophin–glycoprotein complex (DGC) from the sarcolemma. We show that sarcospan (SSPN), a unique tetraspanin-like component of the DGC, ameliorates muscular dystrophy in dystrophin-deficient mdx mice. SSPN stabilizes the sarcolemma by increasing levels of the utrophin–glycoprotein complex (UGC) at the extrasynaptic membrane to compensate for the loss of dystrophin. Utrophin is normally restricted to the neuromuscular junction, where it replaces dystrophin to form a functionally analogous complex. SSPN directly interacts with the UGC and functions to stabilize utrophin protein without increasing utrophin transcription. These findings reveal the importance of protein stability in the prevention of muscular dystrophy and may impact the future design of therapeutics for muscular dystrophies.

Dichlorido[(3,5-dimethyl-1H-pyrazol-1-yl)methane]copper(II)

The title compound, [CuCl2(C11H16N4)], is isostructural with the previously characterized ZnII analogous complex. The CuII ion is four-coordinate in a CuCl2N2 distorted tetrahedral geometry. In the crystal structure, weak C—H...Cl interactions are observed.

Structural Features of a Sulfur-Containing Group 4 Metalla[11]-crown-4 Derivative

Treatment of the ligand system (ο-C6H4OH)-S-CH2-CH2-S-(ο-C6H4-OH) (2a) with TiCl4 gave the metalla-crown ether derivative [(-S-CH2-CH2-S-)(ο-C6H4O)2]TiCl2 (5a). Complex 5a was characterized by an X-ray crystal structure analysis. It showed a pseudo-octahedral structure with both sulfur atoms being cis-coordinated to the metal center. The chloride ligands are also cispositioned, whereas the remaining two Ti−oxygen bonds are trans to each other to complete the distorted octahedral coordination geometry. The reaction of 2a with ZrCl4 gave the analogous complex 5c. The related ligand system (ο-C6H4OH)-O-CH2-CH2-O-(ο-C6H4OH) (2b) was doubly deprotonated by treatment with butyl lithium and then reacted with TiCl4 to yield the complex [(-O-CH2-CH2-O-)(ο-C6H4O)2]TiCl2 (5b).