Recent Progress on Supramolecular Luminescent Assemblies Based on Aurophilic Interactions in Solution

The development of supramolecular systems showing aurophilic interactions in solution is gaining much attention in the last years. This is due to the intriguing photophysical properties of gold(I) complexes, which usually confer to these supramolecular assemblies interesting luminescent properties, as well as the possibility of morphological modulation, through fine tuning of inter- and intramolecular aurophilic interactions, in synergy with the formation of other supramolecular contacts. In this work, an overview of the advances made in this area since 2015 is presented. A large variety of systems showing different spectroscopical and structural topologies has been reported. Moreover, these supramolecular assemblies have proven to be useful in a wide range of applications.

Dual-supramolecular contacts induce extreme Hofmann framework distortion and multi-stepped spin-crossover

A ligand with dual-supramolecular contact character has been exploited to induce extreme Hofmann framework distortion and a resultant multi-stepped spin-crossover transition behaviour with a mismatch between structural and spin-state periodicity.

Intermolecular hydrogen bonding H···Cl in crystal structure of palladium(II)-bis(diaminocarbene) complex

The reaction of bis(isocyanide)palladium complex cis-[PdCl2(CNXyl)2] (Xyl=2,6-Me2C6H3) with excess of 4,5-dichlorobenzene-1,2-amine in a C2H4Cl2/MeOH mixture affords monocationic bis(diaminocarbene) complex cis-[PdClC{(NHXyl)=NHC6H2Cl2NH2}{C(NHXyl)=NHC6H2Cl2NH2}]Cl (3) in moderate yield (42%). Complex 3 exists in the solid phase in the H-bonded dimeric associate of two single charged organometallic cations and two chloride anions according to X-ray diffraction data. The Hirshfeld surface analysis for the X-ray structure of 3 reveals that the crystal packing is determined primarily by intermolecular contacts H–Cl, H–H, and H–C. The intermolecular hydrogen bonds N–H···Cl and C–H···Cl in the H-bonded dimeric associate of 3 were studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method, and estimated energies of these supramolecular contacts vary from 1.6 to 9.1 kcal/mol. Such non-covalent bonding means that complex 3 is an anionic receptor for the chloride anions.

New Crystal Forms for Biologically Active Compounds. Part 1: Noncovalent Interactions in Adducts of Nevirapine with XB Donors

Stabilization of specific crystal polymorphs of an active pharmaceutical ingredient is crucial for preventing uncontrollable interconversion of various crystalline forms, which affects physicochemical properties as well as physiological activity. Co-crystallization with various excipients is an emerging productive way of achieving such stabilization in the solid state. In this work, we identified an opportunity for co-crystallization of antiviral drug nevirapine (NVP) with a classical XB donor, 1,2,4,5-tetrafluoro-3,6-diiodobenzene (1,4-FIB), as well as 1,3-diiodobenzene (1,3-DIB), which has been seldom employed as an XB donor to date. In the X-ray structures of NVP·1,4-FIB and NVP·1,3-DIB co-crystals, different hydrogen and halogen bonding modes were detected and further investigated via DFT calculations as well as topological analysis of the electron density distribution within the framework of the QTAIM method at the M06/DZP-DKH level of theory. Estimated energies of these supramolecular contacts vary from 0.6 to 5.7 kcal/mol.

Tetrachloromethane as halogen bond donor toward metal-bound halides

Two annulated triazapentadiene systems, viz. 1,3,5,7,9-pentaazanona-1,3,6,8-tetraenate chloride complexes of PtII, form CCl4 solvates, containing the Cl3C–Cl···Cl–Pt halogen bonds. These halogen bonds are firstly reported type of Cl3C–Cl···Cl–M contacts. In the X-ray structures of two solvates different non-covalent interactions were detected and studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method at the M06/DZP-DKH level of theory. Estimated energies of these supramolecular contacts vary from 0.6 to 2.4 kcal/mol.

Crystal packing analysis of in situ cryocrystallized 2,2,2-trifluoroacetophenone

Crystals of the liquid compound 2,2,2-trifluoroacetophenone (TFAP, C8H5F3O) were obtained using the state-of-art in situ cryocrystallization technique. TFAP crystallizes in the monoclinic space group C2/c, and its crystal structure is mainly stabilized by a set of C—H...F, C—H...O, F...F and F...O supramolecular contacts. The overall molecular arrangement shows the formation of molecular sheets parallel to the bc plane, which are in turn stacked along the a-axis direction. The weak interactions have been studied thoroughly, performing both a Hirshfeld surface analysis and theoretical calculations, to obtain the intermolecular interaction energies. A structural comparison of this compound with the previously reported substituted analogs was also carried out, showing a qualitative difference in terms of packing behaviour.

The hydrochloride and hydrobromide salt forms of (S)-amphetamine

Despite the high profile of amphetamine, there have been relatively few structural studies of its salt forms. The lack of any halide salt forms is surprising as the typical synthetic route for amphetamine initially produces the chloride salt. (S)-Amphetamine hydrochloride [systematic name: (2S)-1-phenylpropan-2-aminium chloride], C9H14N+·Cl−, has aZ′ = 6 structure with six independent cation–anion pairs. That these are indeed crystallographically independent is supported by different packing orientations of the cations and by the observation of a wide range of cation conformations generated by rotation about the phenyl–CH2bond. The supramolecular contacts about the anions also differ, such that both a wide variation in the geometry of the three N—H...Cl hydrogen bonds formed by each chloride anion and differences in C—H...Cl contacts are apparent. (S)-Amphetamine hydrobromide [systematic name: (2S)-1-phenylpropan-2-aminium bromide], C9H14N+·Br−, is broadly similar to the hydrochloride in terms of cation conformation, the existence of three N—H...Xhydrogen-bond contacts per anion and the overall two-dimensional hydrogen-bonded sheet motif. However, only the chloride structure features organic bilayers andZ′ > 1.

A novel dinuclear MoVIcomplex with tris(3,5-dimethyl-1H-pyrazol-1-yl)methane

Recrystallization of [MoO2Cl{HC(3,5-Me2pz)3}]Cl [where HC(3,5-Me2pz)3is tris(3,5-dimethyl-1H-pyrazol-1-yl)methane] led to the isolation of large quantities of the dinuclear complex dichlorido-2κ2Cl-μ-oxido-κ2O:O-tetraoxido-1κ2O,2κ2O-[tris(3,5-dimethyl-1H-pyrazol-1-yl-1κN2)methane]dimolybdenum(IV) acetonitrile monosolvate, [Mo2Cl2O4(C16H22N6)]·CH3CN or [{MoO2Cl2}(μ2-O){MoO2[HC(3,5-Me2pz)3]}]·CH3CN. At 150 K, this complex cocrystallizes in the orthorhombic space groupPbcmwith an acetonitrile molecule. The complex has mirror symmetry: only half of the complex constitutes the asymmetric unit and all the heavy elements (namely Mo and Cl) are located on the mirror plane. The acetonitrile molecule also lies on a mirror plane. The two crystallographically independent Mo6+centres have drastically different coordination environments: while one Mo atom is hexacoordinated and chelated to HC(3,5-Me2pz)3(which occupies one face of the octahedron), the other Mo atom is instead pentacoordinated, having two chloride anions in the apical positions of the distorted trigonal bipyramid. This latter coordination mode of MoVIwas found to be unprecedented. Individual complexes and solvent molecules are close-packed in the solid state, mediated by various supramolecular contacts.