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In this manuscript, we report the synthesis and X-ray characterization of three N6-aminoacid/peptide–adenine-derivatives; the zwitterion N6GlyAde·0.5H2O (1), its corresponding protonated form N6GlyAde·2HCl·H2O (2) and N6GlyGlyAde·H2O (3). In the zwitterion complex (1), the adenine is protonated at N(3) and the anionic carboxylate interacts with the imidazole ring of the neighbouring purine molecule. It also interacts with the water molecule that connects it to another adenine ring through N(7)–H…O hydrogen bonds. The hydrochloride (compound 2) crystallizes forming a laminar structure and exhibits double protonation in the adenine ring (at N1 and N7). Moreover, energetically strong anion–π interactions are important for constructing the final solid state architecture in 2. Finally, compound 3, which presents a neutral adenine ring, crystallizes in a chiral point group and forms CH…O and CH…N H-bonding interactions in the solid state. We have also studied the noncovalent interactions energetically using DFT calculations and rationalized the interactions using Molecular Electrostatic Potential surfaces and Bader's theory of “Atoms-in-Molecules”. [ABSTRACT FROM AUTHOR]

Two new bromine head-containing oxacalix[2]arene[2]triazines were designed and synthesized. Owing to the bromine head and complementary V-shaped cavity, the solid state structure of oxacalix[2]arene[2]triazine having N,N-dipropylamino substituents showed an intriguing and unique 1D-supramolecular chain-like self-assembly. To provide deep insight into the true nature of the observed stabilizing interactions, i.e., lone pair–π or σ-hole–π interactions, theoretical calculations were carried out. The computations confirm the presence of genuine σ-hole–π interactions. On the other hand, the calculations on the analogous oxacalix[2]arene[2]triazine having chlorine substituents revealed the greater π-acidic character of the s-triazine rings, thus proposing the cleft-like cavity to be more suitable for lone pair–π interactions. This is supported by retrieving the X-ray single crystal structure of the parent oxacalix[2]arene[2]triazine from the CSD which showed the existence of mixed lone pair–π/σ-hole–π and true lone pair–π interactions in the solid state. The study provides constructive clues on the utility of these macrocycles in host–guest and related fields of supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Two novel Cu(ii) complexes, [Cu2L2(μ1.1-N3)2] (1) and [Cu2L2(μ1.1-CH3COO−)2]·2H2O (2), have been synthesized using a tridentate NNO donor Schiff base ligand, 2-[(piperidin-2-ylmethylimino)-methyl]-phenol (HL) and azide or acetate as the co-ligand. Both the structures exhibit elongated (4 + 1) square pyramidal geometries and are centrosymmetric dimers, in which the metal centers are connected by the double μ1.1-azido and acetate bridges. Both complexes exhibit unconventional C–H…π(chelate) interaction along with conventional C–H…π(aryl) supramolecular interactions in the solid-state assembly. A detailed analysis of Hirshfeld surfaces and fingerprint plots elegantly quantifies the interactions within the crystal structures, revealing significant similarities and differences in the interactions experienced by the complexes. The intricate combinations of C–H…π(chelate) and C–H…π(aryl) interactions are fully described along with the computational studies. The binding energies associated with the noncovalent interactions observed in the crystal structures and the interplay between them have been calculated using theoretical DFT calculations. Moreover, the interactions have been characterized by using both Bader's theory of “atoms-in-molecules” and the noncovalent interaction plot (NCI plot). [ABSTRACT FROM AUTHOR]

Three new molecular CT adducts with dihalogens, based on 5,5-dimethyl-2-thiohydantoin (dth) and 1,5, 5-trimethyl-2-thiohydantoin (mdth) donor molecules have been synthesised and characterised by single crystal X-ray diffraction and their crystal structures compared with those of previously published analogous compounds to assess the role of molecular shape of the donors, and cooperativity and competition between hydrogen-bonds (HBs) and halogen-bonds (XBs) in defining the observed supramolecular architectures at the solid state. The study of the role played by these factors was supported by several computational tools. The structural feature at the base of the crystal packings observed is the formation of dimers of donor molecules via complementary N–H…O or N–H…S HBs. These dimers are arranged in space in 2D architectures via further interactions involving the S/Se…I–I/Br XBs. Interestingly, in most of the cases the XB interactions strengthen upon formation of the self-assembled H-bonded dimers, indicating a favourable cooperativity effect which is at the base of the supramolecular architectures formed. [ABSTRACT FROM AUTHOR]

For well over half a century part of the scientific community has been committed to understanding and predicting how molecules recognize each other. This subject of unceasing interest, ‘supramolecular chemistry’, relies on the understanding of noncovalent interactions. Among the noncovalent forces, the anion–π interaction has attracted increasing attention ever since its inception about two decades ago. This highlight article first summarizes some of the fundamental aspects of this interaction leading to several design strategies. In the main body we highlight some relevant examples that illustrate the viability of these strategies and the importance of anion–π interactions in crystal engineering. [ABSTRACT FROM AUTHOR]

In this manuscript we report the synthesis and X-ray characterization of several complexes of Cu(ii), Co(ii) and Ni(ii) with 2-(N-benzimidazolyl)-pyrimidine (L) and nitrate co-ligands. Complexes 1 and 2 are trans and cis isomers, respectively, with formula [CuL2(NO3)2]. Furthermore, complexes 2, [CoL2(NO3)2] (3) and [NiL2(NO3)2] (4) are essentially isostructural with a cis-disposition of the nitrate ligands. In compounds 1–4, the coordination mode of nitrate is terminal bidentate. Finally, during the synthesis of compound 1, a few crystals of a different complex were found and separated manually from the bulk sample and characterized by X-ray diffraction. In this compound (5), the benzimidazole ring of the ligand is oxidized to benzimidazolone (L′) and the formula of this unexpected compound is [CuL′2(H2O)2](NO3)2. Complexes 1 and 5 are characterized by the presence of anion–π interactions that are relevant to the final 3D architecture and packing. In the crystal structures of the five compounds, C–H…O hydrogen bonds, anion–π and π-stacking interactions are described and analysed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. Moreover, some unconventional interactions have been characterized using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Three copper(ii) complexes, [Cu(L1)(H2O)(OClO3)]n (1), [Cu(L1)(N3)] (2) and [Cu(L2)(Cl)(H2O)] (3) [HL1 = 4-chloro-2-((quinolin-8-ylimino)methyl)phenol and HL2 = 2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol], have been synthesized and characterized by elemental analyses, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. The theoretical study, carried out using density functional theory (DFT) calculations, is devoted to the analysis of the interesting supramolecular assemblies in the solid state of the structures, paying especial attention to lp –π and π–π interactions involving the quinolin-8-ylimino moiety. [ABSTRACT FROM AUTHOR]

New chlorido-dimethylsulfoxide-iridium(III), ruthenium(III) and rhodium(III) complexes with the 2-(1Hpyrazol- 1-yl)-pyrimidine (pyrapyr) ligand (OC-6-N1)-[RhIIICl3(DMSO-κS)(pyrapyr)] (1a, N = 3 and 1b, N = 4); (OC-6-N1)-[RuIIICl3(DMSO-κS)(pyrapyr)] (2a, N = 3 and 2b, N = 4) and (OC-6-N1)-[IrIIICl3(DMSO-κS)- (pyrapyr)] (3a, N = 3 and 3b, N = 4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction studies (1a, 1b, 2a, 2b, a disordered crystal 3a/3b and a cocrystal 3a·3b). In all cases, the metal centers show octahedral geometry coordinated to three chloride ligands and one S coordinated dimethylsulfoxide (DMSO-κS). The coordination sphere of the metal is completed by the pyrapyr molecule. Two different coordination modes are observed: (i) the DMSO-κS is opposite to the pyrimidinic N atom (IUPAC nomenclature is OC-6-31 denoted herein as trans); (ii) DMSO-κS is opposite to the pyrazolic N atom (IUPAC nomenclature is OC-6-41 denoted as cis). For Rh(III) the kinetic product (cis) yields the thermodynamic (trans) upon heating a solution of the kinetic product and both isomers have been X-ray characterized. Conversely for Ru(III), both kinetic and thermodynamic complexes have been obtained by using different procedures. Both isomers have been characterized by X-ray crystallography and the kinetic product does not yield the thermodynamic upon heating a solution of the former. Furthermore, the Ir(III) behaves differently, since both isomers are energetically equivalent and both isomers co-crystallize in the solid state. The kinetic/thermodynamic mechanism that yields the different isomers has been studied by using theoretical DFT calculations for each metal. Finally, two Ru(II) complexes (OC-6-N1)-[RuIICl2(DMSO-κS)2(pyrapyr)] (4a, N = 3 and 4b, N = 4) are also described and X-ray characterized. They were obtained as minor products during the synthesis of 2a. [ABSTRACT FROM AUTHOR]

A new dinuclear di(μ-alkoxido) bridged complex [Fe2L2] (1) (H3L = N,N′-bis{1-(2-hydroxyphenyl)-ethylidene}-2-hydroxy-1,3-propanediamine) has been synthesized and characterized. The structure of 1 consists of a centrosymmetric dimer where two crystallographically equivalent metal ions are asymmetrically bridged by two alkoxido oxygen atoms. In the structure, each ligand coordinates to one Fe(iii) centre and consequently the imino nitrogen atoms are in cis positions, which is rather unusual for this ligand. Variable-temperature magnetic susceptibility measurements of the complex indicate that the two iron(iii) centres are antiferromagnetically coupled (J = −17.46 cm−1). The exchange mechanism has been investigated by means of DFT calculations. In addition, the theoretical study has been also used to rationalize the unusual coordination mode of the Schiff base ligand. Moreover, the influence of the weak forces or solvent molecules present in the solid-state structure for the conformational change is also analysed theoretically. This theoretical calculation incorporates two more similar structures, [Fe2LSTACKABOVE′/ABOVEBELOW2/BELOW/STACK]·CH2Cl2 (2) and [Fe2L′2]·2CH3CN (3) (H3L′ = N,N′-bis(salicylidene)-1,3,-diaminopropan-2-ol), for a comparative study. Complex 2 has been reported previously in the literature with the usual binding mode of the ligands. We have repeated its synthesis and recrystallized it from another solvent (acetonitrile) to get complex 3 which is isostructural with 2 but has acetonitrile as solvent molecule. [ABSTRACT FROM AUTHOR]