Search

This manuscript shows that chalcogen bonding (ChB) interactions are enhanced by the coordination of the chalcogen atom to metal centers as evidenced using DFT calculations (PBE0-D3/def2-TZVP level of theory). X-ray structures retrieved from the Cambridge Structural Database (CSD) are used to support the enhanced ability of Se and Te-atoms coordinated to transition metals to participate in ChBs, eliminating the necessity to use strong electron-withdrawing groups bonded to the Ch atom. Orbital analysis performed using the natural bond orbital (NBO) technique discloses a large LP → σ* contribution, especially for anionic electron donors. In one example, the new σ-hole that is generated upon complexation (opposite to the Ch--M bond) plays a crucial role in the solid state, promoting the formation of infinite 1D polymers. [ABSTRACT FROM AUTHOR]

This manuscript evidences the existence and importance of spodium bonds (SpB) in solid state structures involving five-coordinated square-pyramidal Zn(II) spodium atoms. Four families of compounds have been found analysing the Cambridge structural database (CSD) where the interaction is very important to understand the crystal packing: (i) multi-dentate Schiff-base complexes, (ii) Zn-porphyrins, (iii) aza-crown ethers and (iv) polyoxometalates, the latter as SpB acceptors. The square-pyramidal around the metal center facilitates the approximation of the electron rich atom (ElR) to the Zn(II), contrariwise to the four-coordinated tetrahedral geometry where the steric crowd of the Zn ligands usually impedes the formation of the SpB. This highlight concentrates on the SpB interaction, which is different from the classical coordination bond in the sense that Y–Sp⋯A distances are longer (around the sum of van der Waals radii), the interaction weaker and it involves the σ* orbital of the Y–Sp bond (Y = any atom). A theoretical study on one representative family of compounds (Zn-porphyrins) has been also carried out indicating that the SpB energies range from −1 to −7.4 kcal mol−1. Finally, a statistical analysis of the CSD evidences that the interaction can be somewhat directional. [ABSTRACT FROM AUTHOR]

Developing chemosensors for efficient detection of Al3+ and picric acid in water is in high demand but challenging. In this paper, we have demonstrated the potential of a probe, 6,6′-(1E,1′E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-methoxyphenol) (H2Vm), as a “switch-on” Al3+ responsive fluorescence chemosensor in water. In addition to the ability of H2Vm to sense Al3+, the Al2-Vm2 complex offers selectivity towards picric acid (PA) in HEPES buffer (pH = 7.4) solution (detection limit (20.13 × 10−9 M) via“switch-off” mode. The reversible fluorescence response with low detection limit (11.34 × 10−9 M) in the pH range of 6.0–9.0 makes H2Vm suitable for tracking Al3+ in live HCT cells. The resulting Al2-Vm2 complex is also responsive towards PA in HCT cells. Thus, a versatile fluorescence spectroscopy-based chemosensor for Al3+ and picric acid has been developed with possible applications in human health and national security. [ABSTRACT FROM AUTHOR]

Five new Pb(ii) complexes of hydrazone-based and Schiff-based ligands and three different anionic co-ligands (azide, thiocyanate and bromide) have been synthesized and characterized by structural, analytical and spectroscopic methods. This variety of ligands can coordinate to the Pb(ii) metal center in a tridentate or tetradentate fashion via a different combination of any of nitrogen, oxygen and sulphur donor atoms. Moreover, the organic ligands can be in mono-deprotonated or neutral forms. By using single-crystal X-ray crystallography, we show that the synthesized complexes aggregate into larger supramolecular entities due to the formation of noncovalent tetrel bonding interactions. The Pb(ii) center is hemidirectionally coordinated even in those complexes where the coordination number is six. Consequently, this is sterically ideal for establishing tetrel bonding interactions with electron-rich nitrogen, bromide or sulphur atoms. These contacts are significantly larger than the sums of the covalent radii. Hence, they can be described as non-covalent tetrel bonding interactions. They interconnect the covalently bonded units into supramolecular assemblies (dimers or tetramers). The contribution of contacts involving the Pb atom has been studied using Hirshfeld surface analysis and fingerprint plots. We have analysed the supramolecular assemblies observed in the solid state by means of DFT calculations and characterized them using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Combining computations and X-ray structure analysis we have demonstrated that [Pt(CN4)]2− can behave as a Lewis acid inside an enzyme's cavity. The nature of a counterintuitive contact found between a catalytically active GLN residue belonging to a mitochondrial synthase and the Pt(II) center was investigated by combining molecular dynamics and quantum mechanics calculations. Results confirm the electron acceptor role of [Pt(CN4)]2−, serving as an inspiration for the design of biomolecular cages able to tweak the nucleophilic/electrophilic character of an organometallic compound. [ABSTRACT FROM AUTHOR]

Crystal structures of aminopyridine–succinate salts (1–3) were solved by single crystal X-ray diffraction where salt bridge (SB) interactions between the succinate and protonated aminopyridine dominated their supramolecular architecture. X-ray crystallography reveals that compounds 1 (hydrogensuccinate 2-amino-5-methylpyridinium salt) and 2 (hydrogensuccinate 2-amino-4-methylpyridinium salt) exhibit C–H…SB…π+ assemblies, while compound 3 (succinato-aminopyridinium salt) displays unique N–H…SB…lone pair (l)p networks in the solid state. These unexplored extended networks are described and investigated for the first time in crystalline structures. Our study also describes the duality of the salt bridge in establishing π-facial interactions with electron rich and/or electron poor moieties depending on the positive or negative nature of the SB counterpart that interacts with the SB surface. The theoretical study combines an energetic investigation of the noncovalent forces that contribute to the extended supramolecular network and the characterization of the diverse interactions by means of Bader's theory of “atoms in molecules” (AIM) and the NCIplot index. [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]

A supramolecular motif listed as ‘carbon bonded’ or ‘hydrogen bonded’ may have the character of both. We highlight the hybrid character of the non-covalent interaction in a bis-Schiff base of N-allyl isatin by theoretical studies, the solid state structure of which is mainly driven by a non-covalent carbon/hydrogen bonded self-complementary dimeric {…C–N–C=O/H–C–N–C=O}2 synthon. [ABSTRACT FROM AUTHOR]

In this manuscript, we report the design, synthesis and X-ray characterization of nitrodiene derivatives that present crucial π–hole interactions involving the nitro group as a π–hole donor. The solid state structures of 1,4-dinitro-1,3-butadiene (1), its co-crystal 1·Diox, and homologous 1,4-dinitro-1,3-pentadiene (2) and 2,4-dinitro-2,4-hexadiene (3) feature competition of lone pair–π–hole interactions with common weak CH…O bonding and gradually increased role of the NO2…NO2 interactions. Regular evolution of the supramolecular patterns (1 to 3) results in generation of an unprecedented 3D non-covalent framework in 3 that is controlled exclusively by short π–hole contacts (O…N = 2.9615(18), 3.1304(18) Å). These findings complement the results of high level ab initio calculations (MP2/def2-TZVP) and unite theory and experiment, thus supporting the functional relevance of this novel π–hole interaction. [ABSTRACT FROM AUTHOR]

A novel ambiguous reactivity of Li/Cl phosphinidenoid complexes under redox conditions is described. The outcome of the reaction with hexafluoroacetone is highly dependent on the P-substituent as fluoride substitution occurred in the case of R = CPh3 and C5Me5via a radical pathway, whereas for R = CH(SiMe3)2 a complex having a novel 1,2-diol-type P-ligand was obtained via a closed-shell pathway. DFT calculations reveal a new SET pathway starting with a noncovalent π-hole complex between the phosphinidenoid anion and hexafluoroacetone followed by an elimination of LiF. The second, closed-shell reaction course is strongly influenced by a noncovalent O…Si interaction established after the initial nucleophilic attack. [ABSTRACT FROM AUTHOR]

In this study, nine mercury(ii) complexes of the composition [Hg(Ln)(X)2] (X = Cl, Br and I, n = 1–3), (L1 = 2-pyridine piconyl hydrazone); L2 = (2-acetylpyridine piconyl hydrazone) and L3 = (2-phenylpyridine piconyl hydrazone) are synthesized and spectroscopically characterized. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Moreover, Hirshfeld surface (HS) analyses were employed to gain additional insight into interactions responsible for the packing of complexes 1–9. Quantitative examination of 2D fingerprint plots revealed, among others, the dominating participation of H…H and H…X interactions in the molecular packing. Moreover, C–H…X hydrogen bonds, π–π, and chelate-ring–π 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. The influence of the halide on the energetic features of the assemblies has been also studied. [ABSTRACT FROM AUTHOR]

A theoretical study of nitryl halide heterodimers has been carried out using SCS-RI-MP2 and CCSD(T) at the complete basis set (CBS) calculations. For this purpose, 66 heterodimers have been characterized as minima and arranged in six groups depending on the interactions involved and their geometrical arrangements. The CCSD(T)/CBS interaction energies vary between −0.6 and −11.1 kJ mol−1. The heavier the halogen atoms, the larger the interaction energies. Natural bond orbital (NBO) and “atoms-in-molecules” (AIM) theories were then used to analyze the complexes, confirming the presence of halogen, chalcogen, and π-hole interaction bonds. The largest charge-transfer energy contributions were found for halogen bonded complexes (up to 29.1 kJ mol−1). Furthermore, the physical nature of the interactions was studied using symmetry-adapted perturbation theory (SAPT) calculations, and it was concluded that dispersion was the major source of attraction, although electrostatics is important in halogen bonded complexes. [ABSTRACT FROM AUTHOR]

A new series of six structurally diverse lead(ii) coordination compounds was assembled from two isomeric nicotinoylhydrazones as neutral ligands and three Pb(ii) salts with different monoanions (chloride, nitrate and thiocyanate) as starting materials. The products were isolated in good yields and were fully characterized, including by single-crystal X-ray diffraction and theoretical methods. Within the six compounds, three feature 2D metal–organic networks, two are 1D coordination polymers, and another one comprises discrete 0D dimeric units. The structures of the latter low dimensional compounds are extendable into 2D supramolecular networks. The topology of the coordination or supramolecular networks is primarily dictated by the geometry of the nicotinoylhydrazone used as a main building block. In contrast, supramolecular interactions are greatly influenced by the choice of the anion in the starting lead(ii) salt, which is demonstrated by Hirshfeld surface analysis. In fact, the topological analysis and classification of metal–organic or supramolecular underlying networks in the obtained compounds was performed, disclosed the hcb, 2C1, gek1, SP 1-periodic net (4,4)(0,2) and 3,4L83 topological types; the latter topology was documented for three compounds, including both coordination and supramolecular networks. In the two compounds containing thiocyanate moieties, there are supramolecular contacts between the thiocyanate anions and lead centres. These were shown by DFT calculations to be strong tetrel bonds (−15.3 and −16.7 kcal mol−1) between the σ-hole of the lead atom and the π-system of the thiocyanate S–C bond. [ABSTRACT FROM AUTHOR]

Four Pb(ii) complexes of (iso)nicotinohydrazide-based ligands and different anionic coligands (azide, nitrate, acetate and iodide) have been synthesized and characterized by structural, analytical and spectroscopic methods. The mono-deprotonated or neutral forms of the ligands coordinate in a tridentate fashion via two nitrogen and one oxygen donor atoms to the Pb. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. In all four complexes the lead center is hemidirectionally coordinated and, consequently, it is sterically ideal for establishing tetrel bonding interactions. In the crystal structures of all complexes, the lead atoms participate in short contacts with nitrogen atoms. These contacts are shorter than the sums of the van der Waals radii and larger than the sums of the covalent radii. The tetrel bonding interactions interconnect the covalently bonded units (monomers or dimers) into supramolecular assemblies (chains and 3D structures). We have analysed the interesting supramolecular assemblies observed in the solid state of all four complexes by means of DFT calculations. [ABSTRACT FROM AUTHOR]

In this manuscript we report for the first time the concurrent agostic and tetrel bonding interactions involving the heaviest tetrel atom (Pb) in N′-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide–PbX complexes (X = Cl, I, NCS, NO2). [ABSTRACT FROM AUTHOR]

In this manuscript we report the synthesis and X-ray characterization of five complexes of Zn(ii) based on a N4O core carbohydrazone ligand (H2L); i.e. {[Zn4(HL)4](CH3OH)4(NO3)4} (1), {[Zn4(HL)4](ClO4)4} (2) {[Zn4(HL)4][Zn(SCN)4](NO3)2} (3) {[Zn(SCN)4](H4L)(CH3OH)2} (4) and {[Zn4(HL)4](NO3)4(H2O)} (5). Structurally characterized tetranuclear Zn(ii) complexes, as those reported herein, are scarcely found in the literature. In the crystal structures of several compounds, N–H…S hydrogen bonds, anion–π and π–hole 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, the noncovalent interactions have been also analysed using Hirshfeld surface analysis. [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]

We have recently communicated [CrystEngComm, 2015, 17, 1769–1772] the synthesis and X-ray characterization of several oxaphosphirane tungsten(0) complexes especially designed to analyse the intramolecular W–CO(lone pair)…π(arene) interaction varying the degree of fluorination in the arene. Unexpectedly, the phenyl-substituted oxaphosphirane complex showed the shortest CO…π distance in the solid state which is very close to that observed for the pentafluorophenyl derivative. Other complexes with two or three fluorine substituents exhibited longer distances. We rationalized the affinity of the M–CO moiety for both electron-rich and electron-deficient rings by considering that the interaction can be also understood as a π–π interaction where the negative part of the CO is dominant in the π-acidic arene and the positive part of the CO is dominant in the π-basic arene. This explanation was supported by DFT calculations using orbital analysis and Bader's theory of “atoms-in-molecules”. Herein, we expand the previous study with new theoretical results of some model complexes to gain insight into the energetic and geometric features of the interaction. The experimental behaviour of the 31P-NMR chemical shifts of the title compounds agrees well with previous theoretical explanation of the physical nature of the interaction. Furthermore, we analyse the crystal packing of the four X-ray structures previously communicated in order to scrutinize other interactions in the solid state that may influence the W–CO…π interaction. Finally, stronger intermolecular interactions that influence the crystal packing are also analysed using DFT calculations. [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]

A CSD analysis and DFT study reveal that the nitrogen lone-pair in [N(PPh3)2]+ is partially intact and involved in intramolecular hydrogen bonding. Computations with the model cation [N(PMe3)2]+ indicate that intermolecular hydrogen bonding with this ion's N-atom is possible (−8.3 kcal mol−1 for H2O as hydrogen bond donor), presenting a rare example of pseudo anti electrostatic hydrogen bonding. [ABSTRACT FROM AUTHOR]

We report the synthesis and X-ray characterization of several oxaphosphirane tungsten(0) complexes especially designed to analyse the intramolecular W–CO(lone pair)…π(arene) interaction. The unexpected behaviour of this interaction in the solid state of oxaphosphirane complexes with different degrees of fluorination is rationalized by means of DFT calculations using orbital analysis and Bader's theory of “atoms-in-molecules”. [ABSTRACT FROM AUTHOR]

A combined CSD and ab initio study reveals that the interaction between the sp³ C-atom in para-substituted ArCF3 and electron rich atoms is weak (<5 kcal mol-1), somewhat directional, and thus comparable to CH-π interactions. [ABSTRACT FROM AUTHOR]

Five new proton transfer compounds, (bimipyrH2)(Cl)2 (1), (bimipyrH2)[(NO3)(NO3HNO3)] (2), (bimipyrH2)(ZnCl4) (3), (bimipyrH2)(CdCl4) (4) and (bimipyrH2)(HgCl4) (5) (bimipyr = 4,6-di(1H-imidazol-1-yl)pyrimidine), have been synthesized and characterized by elemental analysis, IR and NMR spectroscopy and single crystal X-ray diffraction. Crystallographic analysis revealed that the asymmetric unit of 1 consists of one doubly protonated bimipyr molecule, one solvent water molecule and two chloride anions. Conversely, 2 is anhydrous where one counterion is chelated by the (bimipyrH2)2+ molecule and the other anion is solvated by the parent acid forming an independent 'acid salt' counterion [NO3HNO3]-. Both compounds exhibit diverse architectures involving hydrogen bonding and anion-π interactions. Compounds 3, 4 and 5 consist of outer sphere complexes of diprotonated bimipyr with [MCl4]2- as the counterion. They have the same molecular composition and compounds 4 and 5 (M = Cd and Hg, respectively) are essentially isomorphous and crystallized in the monoclinic space group P21/n. In the crystal structures of the five salts, N-H⋯Cl/O and C-H⋯Cl/O hydrogen bonds as well as anion-π, involving aromatic rings and inorganic anions, 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. Finally, aggregation studies of compound 1 in solution (DMSO) are also described and discussed. [ABSTRACT FROM AUTHOR]

A novel type of C–H/σ supramolecular interaction involving σ-aromatic M2X2 (M = Cu, Hg; X = Cl, Br, I, S) cores is reported for the first time. Three new polymeric coordination copper complexes, {[Cu(μ-Cl)(Cl)- (μ-L)]2}n (1), {[Cu(μ-I)(μ-L)]2}n (2) and [Cu(Br)2(μ-L)(CH3CN)2]2 (3), have been synthesized with the organic ligand α,ω-bis(benzotriazoloxy)propane system (L) and halides as counterions. A very interesting C–H/σ supramolecular interaction has been observed in the solid state structure of compound 2, similar to a C–H⋯π interaction, which has been confirmed by Bader’s “atoms-in-molecules” AIM analysis. The Nucleus Independent Chemical Shift (NICs) method was used to evaluate the aromatic character of the different cores in this study. The influence of the nature of the metal ions, bridging atoms, oxidation states, and coordination environments around the metal centers on the strength of the aromaticity of the M2X2 cores was theoretically analyzed and explained. The binding ability of the 1-alkoxy-1,2,3-benzotriazole ring to establish π–π and C–H/π interactions and how its coordination to Cu(I) and Cu(II) ions affects the strength of the aforementioned interactions have been discussed. The electron deficient triazole ring and its π-acidity increases upon coordination of the Cu ion, leading to the formation of a lone pair (lp)–π interaction involving the five-membered ring of the ligand, which has also been analyzed. We have also analyzed the C–H/σ interactions of previously reported X-ray crystal structures of different coordination polymers based on a binuclear copper(I) complex and 2,3-dimethylpyrazine, dithioethers, and benzotriazol- 1-yl-based pyridyl units as ligands using I− as a counter-ion. Complex 1 shows antiferromagnetic behavior with a magnetic coupling constant of J = −7.9 cm−1. Moreover, photoluminescence and TGA studies of the complexes were also carried out. [ABSTRACT FROM AUTHOR]

In 1996 J. Derek Woollins reported “π-facial” interactions between the chloride anion and the seven-membered aromatic [S4N3]+ and inorganic ring (Polyhedron, 1996, 15, 4603–4605). In spite of this manuscript has not been highlighted before (only 5 citations so far), it can be considered as a pioneering work in the field of noncovalent interactions involving anions, since unprecedented anion–π contacts were described as “π-facial” interactions. In this manuscript several complexes of [S4N3]+ with anions were optimized at the BP86-D3/def2-TZVPD level of theory and compared to X-ray structures retrieved from the CSD. We have evaluated the interaction energies between the chloride and nitrate anions and the [S4N3]+ ring. The anion–π complexes are energetically favourable and the complexation has been characterized by means of Bader's theory of “atoms in molecules”. Moreover, the π-orbitals of the [S4N3]+ ring have been computed and the aromaticity of the 10-π electron seven membered ring was analysed. [ABSTRACT FROM AUTHOR]

A statistical survey of the Cambridge Structural Database reveals that the interaction between the π-holes of nitro groups and electron-rich atoms is somewhat directional. High-level ab initio computations indicate energies up to −6.6 kcal mol−1. [ABSTRACT FROM AUTHOR]

Herein we report the experimental observation (X-ray characterization) of two different binding modes in H-bonded anion–anion complexes (anion = citrate) in N-(1-(2-phenylethyl)-4-piperidinylium)-N-phenyl-propanamide-citrate (fentanyl citrate). High level DFT calculations indicate that both types of anion–anion complexes (one with two and the other with four H-bonds) are thermodynamically unstable but kinetically stable with respect to the isolated anions with activation barriers as high as 14 kcal mol−1. [ABSTRACT FROM AUTHOR]

A mixed valence cobalt(iii/ii) complex, [(μ1,3-OAc)2{(SCN)CoIII(L1)}2CoII]·H2O (1), and an ionic coordination complex of cobalt(iii), [CoIII(L2)2][CoIII(L2)(N3)3] (2), have been synthesized and characterized {H2L1 = N,N′-bis(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine and HL2 = N(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine}. Energetic features of the supramolecular interactions involved in both complexes have been studied through DFT calculations, which indicate that the trinuclear structure of complex 1 has been stabilized viaσ-hole halogen bonding interactions in the solid state. On the other hand, counterintuitive anion…anion interactions are present in the solid state structure of complex 2, which have been stabilized through anti-electrostatic H-bonds (AEHB). The dissociation scan plot for the AEHB dimer has showed the existence of a significantly high energetic barrier. [ABSTRACT FROM AUTHOR]

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 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]

Four new Pb(ii) complexes of nicotinoylhydrazone and picolinoylhydrazone-based ligands and three different anionic co-ligands (acetate, thiocyanate and iodide) have been synthesized and characterized by structural, analytical and spectroscopic methods. The ligands coordinate to the Pb(ii) metal center in a tridentate fashion via two nitrogen and one oxygen donor atoms either in mono-deprotonated or in neutral forms. Single-crystal X-ray crystallography reveals that the molecular complexes aggregate into larger entities depending upon the anion coordinated to the metal centre. The Pb(ii) center is hemidirectionally coordinated and, consequently, it is sterically ideal for establishing tetrel bonding interactions. Consequently, in the crystal structures of all the complexes, the Pb participates in short contacts with nitrogen, iodide or sulphur atoms. These contacts are shorter than the sums of the van der Waals radii and larger than the sums of the covalent radii, therefore they can be defined as non-covalent tetrel bonding interactions. They interconnect the covalently bonded units (monomers or dimers) into supramolecular assemblies (1D infinite chains and 3D structures). Hirshfeld surface analysis and fingerprint plots have been used to analyse the contribution of contacts involving the Pb atom. We have analysed the interesting supramolecular assemblies observed in the solid state of all four complexes by means of DFT calculations and characterized them using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Four hetero-dinuclear nickel(ii)/lead(ii) complexes have been synthesized and characterized. Their structures have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 compartment and lead(ii) in the outer O2O2′ compartment of the respective Schiff base. In complexes 1, 3 and 4, lead(ii) centres are hemidirectionally coordinated, and thus are well suited for establishing tetrel bonding interactions which have been investigated thoroughly by means of DFT calculations. [ABSTRACT FROM AUTHOR]

A water molecule is encapsulated in a dimeric assembly of a copper(ii) Schiff base complex with a Cu2(NCS)4 moiety. The structure has been confirmed by single crystal X-ray diffraction analysis. Thermogravimetric analysis has been performed to check the stability of the enclathrated water molecule. This theoretical study is devoted to analyzing the stabilization of the H2O molecule in the cavity generated by the formation of the supramolecular dimer of the copper(ii) Schiff base moiety in the solid state. The Cu2(NCS)4 moiety exists as a bimetallic eight-membered ring, which behaves as a π-system establishing C–H…π interactions with two neighbouring copper(ii) Schiff base moieties. The molecular electrostatic potential (MEP) surface of the complex has been computed to rationalize the interaction from an electrostatic point of view. [ABSTRACT FROM AUTHOR]

In recent years, the crystal engineering library has been enriched with a number of previously unrecognized or unnoticed intermolecular interactions, such as agostic, tetrel, chalcogen, pnicogen bonding and chelate ring stacking – collectively referred to as “unconventional interactions”. Many open questions remain unaddressed regarding their ability to form synthon interactions, specificity, and cooperativity, for example with π–π stacking interactions. In this work, we throw light on the formation of chelate ring stacking in metal–organic assemblies of nicotinohydrazide ligands (N′-(1-(2-pyridyl)ethylidene)nicotinohydrazide (HL) and N′-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HL1)) with mercury(ii) halide (HgBr2, HgI2) salts. Their reaction produced five compounds, namely [Hg(μ-L)BrHgBr2]n (1), [Hg(μ-L1)Br]n (2), [Hg(L)I2] (3), [Hg(HL1)I2]·(CH3OH) (4), and [Hg(μ-L1)I]n (5). Crystal structure analysis reveals that chelate ring stackings are formed in four of the reported metal–organic compounds, and are common also in the literature precedents. The energies of chelate ring stackings and π–π heterocycle stackings have been computed and analyzed by means of DFT calculations, and the results were verified using Bader's theory of “atoms in molecules”. These results provide a rationale for preferential formation of both unconventional and conventional stackings and allow us to conclude that chelate ring interaction may be considered as a synthon interaction for nicotinohydrazide metal complexes. Interpretations for packing differences imposed by the substituent effect (substitution of methyl group in HL for phenyl group in HL1) were provided based on the Hirshfeld surface analysis and 2D fingerprint plots of the crystal structures reported here. [ABSTRACT FROM AUTHOR]

Three heteronuclear cobalt(iii)/sodium Schiff base complexes have been synthesized and characterized by elemental and spectral analysis. The structures of all three complexes have been confirmed by single crystal X-ray analyses. Each of these three complexes crystallizes in monoclinic space group P21/c. In each complex, cobalt(iii) is placed in the inner N2O2 compartment and sodium is placed in the outer O2O′2 compartment (O and O′ denote the phenolic and ethoxy/methoxy oxygen atoms, respectively) of the Schiff bases. With decrease in steric hindrance around the O2O′2 compartment by the replacement of ethyl groups with methyl groups, tetranuclear complexes resulted instead of dinuclear ones. Interesting carbon bonding interactions in the solid state of the complexes have been studied by means of DFT calculations using several computational tools such as “atoms-in-molecules” (AIM) and natural bond orbital (NBO) analyses. [ABSTRACT FROM AUTHOR]

Variable temperature magnetic measurements of a novel tetranuclear nickel(ii) complex, consisting of two pseudo-dinuclear entities bridged by an end-to-end azide, indicate the presence of both intra- and inter-dinuclear ferromagnetic interactions (J1 = 16.48 cm−1 and J2 = 24.17 cm−1, respectively), as also corroborated by DFT calculations (J1 = 12.0 cm−1 and J2 = 29.2 cm−1). [ABSTRACT FROM AUTHOR]

A novel mononuclear Mn(iii) complex, [MnIII(L1)Cl(H2O)]·H2O (1), and a tetranuclear Zn(ii)–Mn(ii) complex, [{ZnII2(L2)2Cl2}MnII2(μ1,1-N3)2(H2O)2]·2H2O (2), have been synthesized involving azo Schiff base ligands, viz. H2L1 = (E)-6,6′-((1E,1′E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxy-4-((E)-p-tolyldiazenyl)phenol) and H2L2 = (E)-6,6′-((1E,1′E)-((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(2-methoxy-4-((E)-p-tolyldiazenyl)phenol), respectively. The solid-state structures were determined by single crystal X-ray crystallography. In complex 1, the Mn(iii) centre adopts slightly distorted octahedral geometry, while in complex 2 the Mn(ii) centre residing in the outer core of the ligand adopts a distorted pentagonal bipyramidal geometry. In complex 1, the chloride ion simply acts as a terminal coligand, while in complex 2, azide ions bind the metal centres in an end-on bridging fashion to produce a tetranuclear complex. The phenoxazinone synthase-like activity of both complexes has been examined and a detailed investigation of the structure–property correlation has been performed. Whereas the mononuclear complex 1 exhibits significant phenoxazinone activity, complex 2 is almost inactive, although in both complexes labile sites are available at manganese centres for substrate binding. The present work therefore highlights the importance of higher oxidation states of manganese over nuclearity for the development of better in vitro catalysts. In addition, extensive efforts have been made to visualize and quantify all supramolecular interactions present in 1 and 2. [ABSTRACT FROM AUTHOR]

Herein we report the first X-ray solid state characterization of a Ag(i) complex with cytidine-5′-monophosphate (HCMP) of the formula Ag(HCMP)·H2O. The coordination of Ag(i) to HCMP is via both the N3 and O2 atoms of two cytosine moieties and the phosphate group. The short Ag(i)–Ag(i) distances (2.99 Å) suggest an interesting argentophilic attraction as a stabilization source of the final solid state structure along with ancillary O…Ag, H-bonding and π…π interactions that have been rationalized using DFT calculations. [ABSTRACT FROM AUTHOR]

Three metallamacrocycles and one coordination polymer were obtained by using coordination driven self-assembly of the HgI2 salt with four different ligands: 2,2′-butan-1,4-diylbis(oxy)dianiline (L1), 1,4-bis(2′-formylphenyl)-1,4-dioxabutane bis(isonicotinoylhydrazone) (L2), (E)-N′-(pyridin-3-ylmethylene)isonicotinohydrazide (L3) and (E)-1-(pyridin-3-yl)-N-(pyridin-3-ylmethyl)methanimine (L4). The coordination compounds were studied by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction analyses. Reaction of the HgI2 salt with L1, L2 and L3 yields metallamacrocycles of formula [(HgI2)2(μ-L1)2] (1), [(HgI2)2(μ-L2)2] (2), [HgI2(μ-L3)]4 (3). In contrast, the reaction with L4 under the same conditions yields a coordination polymer of formula [{HgI2(L4)}]n (4). In addition, the X-ray structure of L2 is also reported. The influence of the flexibility of the ligand on the final shape and nuclearity of the macrocycle is also analysed. Hirshfeld surface analysis and fingerprint plots facilitate a comparison of intermolecular interactions in all compounds, which are crucial in the construction of the supramolecular architectures. Finally, some noncovalent interactions have been evaluated energetically using DFT calculations and characterized using Bader's theory of atoms-in-molecules. [ABSTRACT FROM AUTHOR]

Reaction of tetrameric trimethylplatinum(iv) iodide with an excess of 3-substituted pyridines in chloroform afforded mononuclear complexes, [PtMe3L2I] (L = 3-CNpy, 3-Brpy, 3-MeOpy, 3-Mepy and 3-Etpy). The complexes were characterized by 1H NMR, CHN analysis and X-ray single crystal structure analysis. The mononuclear complexes undergo reaction with trimethylplatinum(iv) iodide in chloroform to form the corresponding dinuclear forms (both syn and anti). A comparison of both the mononuclear and dinuclear forms in solution for a particular pyridine substituent has been studied in detail with the help of 1H NMR spectroscopy, ably supported by DFT computational studies. The investigation further shows the influence of the pyridine substituent on controlling the mode of the reaction. The crystal structures of two dinuclear complexes, syn-[PtMe3(3-CNpy)I]2 and anti-[PtMe3(3-Brpy)I]2, have also been described here. [ABSTRACT FROM AUTHOR]

Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)2] (1), [(SCN)(CH3CO2)Cd(L)Ni(CH3OH)2] (2) and [(SCN)(Cl)Cd(L)Ni(NH2CH2CH2CH2NH2)]n (3) {where H2L = N,N′-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N2O4 compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N2O2 environment and cadmium(ii) is placed in the outer O4 compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C–H…π (chelate) interactions in the solid state of both complexes and C–H…π (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2–6 ns. [ABSTRACT FROM AUTHOR]

Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (1), [(CuLR)2Zn(NCS)(μ1,1-NCS)] (2) and [(CuLR)2Cd(μ1,3-NCS)2] (4) have been synthesized using [CuL] and [CuLR] as “metalloligands” (where H2L = N,N′-bis(salicylidene)-1,3-propanediamine and H2LR = N,N′-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar “metalloligands” [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex 2, the two terminal “metalloligands” [CuLR] are square pyramidal, as one of the SCN− ions makes an unusual μ1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a usual fashion making its geometry also square pyramidal. For 4 which possesses an angular trinuclear structure, in addition to double phenoxido bridges from two terminal [CuLR], both the SCN− ions are S-bonded to Cd(ii) and form a bridge (cis-μ1,3-SCN) between Cd(ii) and each of the terminal Cu(ii) ions. This structure is different from its unreduced analogue in which NCS− was N-terminal coordinated to Cd(ii) (3/3′). All the structures have been optimized using density functional theory (DFT) calculations. It has been found that for H2L, optimized structures like 1 and 2 differ only by 0.4 kcal mol−1 but the H2LR structure 2 is more stable by 5.5 kcal mol−1 than the structure resembling 1. For Cd(ii) complexes also, H2L optimized structures such as 3 and 4 do not differ significantly in energy (1.0 kcal mol−1) but the H2LR structure 4 is more stable than that of 3 by 4.6 kcal mol−1. In fact, structure 4 has been found to be the most stable one among the other possible isomers of H2LR. [ABSTRACT FROM AUTHOR]

Three Cu and one Co complexes of three pyridine-2,6-dicarboxylic acid derivatives were synthesized by proton transfer reactions. They are formulated as {Cu[(ampym)(hypyafc)(H2O)]}⋅H2O (1), {[Co(pyzdc)(H2O)2]⋅H2O}n (2), [Cu(d/p/c)(µ-dipic)Cu(ii)(H2O)5]⋅2H2O (3) and [Cu3(dipic)4(en)2]⋅enH2⋅4H2O (4) where ampym = 2-amino-4-methylpyrimidine, hypydc-4-hydroxypyridine-2,6-dicarboxylic acid, pyzdc = pyrazine-2,3-dicarboxylic acid, dipic = pyridine-2,6-dicarboxylic acid, en = ethylenediamine. The complexes have been characterized by single crystal X-ray diffraction. Complex 1 is five-coordinated with a distorted square pyramidal geometry around Cu(II) where hypydc acts as a tridentate ligand, ampym as a monodentate ligand and one water molecule coordinated in the axial position. Complex 2 is a linear polymer containing a six-coordinated Co(II) metal center, which is surrounded by N and O atoms from two pyzdc ligands and two coordinated water molecules. Complex 3 is a binuclear compound containing two six-coordinated Cu(II) ions, one coordinated to two dipic ligands while the other one is coordinated by five water molecules and one oxygen atom belonging to the bridging carboxylate group. Complex 4 is a trinuclear complex where two identical ions are hexa-coordinated to four carboxylate groups belonging to two dipic ligands and central ion is coordinated to two ethylenediamine ligands and two oxygen atoms of the dipic ligands. The non-covalent interactions that play important roles in the stabilization of the crystal structures have been analysed for several compounds by means of Density Functional Theory (DFT) calculations and characterized using the Bader's theory of "atoms in molecules" (AIM). The evaluation of the binding energies associated to each noncovalent interaction is useful for rationalizing their influence in the crystal packing. The formation of an unprecedented lp-π-hole interaction in 1 is remarkable. [ABSTRACT FROM AUTHOR]

Two new trinuclear hetero-metallic copper(II)-cadmium(II) complexes [(CuL)2Cd(NCS)2] (1) and [(CuLR)2Cd(SCN)2] (2) have been synthesized using [CuL] and [CuLR] as ''metalloligands'' (where H2L = N,N'-bis(salicylidene)-1,4-butanediamine and H2LR = N,N'-bis(2-hydroxybenzyl)-1,4-butanediamine) respectively. Both the complexes were characterized by elemental analysis, various spectroscopic methods and single crystal XRD. Complex 1 is an angular trinuclear species, in which two terminal four-coordinate square planar ''metalloligands'' [CuL] are coordinated to a central Cd(II) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal thiocyanate ions. In complex 2, which is linear, in addition to the double phenoxido bridge, two SCN- coordinate to the trans positions of the central octahedral Cd(II) via S atoms. Theoretical calculations on the energetic difference between the two possible coordination modes of the thiocyanate anion to the Cd atom reveal that N-coordination is preferred over S-coordination in agreement with the much greater abundance of the reported N-bonded structures. In 2, there is a strong N-H . . . NCS-Cd H-bonding interaction, the binding energy of which is computed to be approximately -9.3 kcal mol-1, which is sufficient to compensate the 9.0 kcal mol-1 of energetic cost due to the unusual Cd-SCN coordination mode. [ABSTRACT FROM AUTHOR]

Two dinuclear [Ni2L2(o-(NO2)C6H4COO)2(H2O)] (1), [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) complexes and one trinuclear [Ni3L2(p-(NO2)C6H4COO)4]·C2H5OH (3) Ni(II) complex have been synthesized using a tridentate Schiff base ligand, 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) along with ortho- and para-nitro benzoate as co-ligands. All these three (1–3) complexes have been characterized by spectral analysis, X-ray crystallography and variable temperature magnetic susceptibility measurements. The structural analyses reveal that complexes 1 and 2 are dinuclear in which two μ2-phenoxido and a water molecule bridge the two Ni(II) centers to make the complexes face sharing bioctahedra. Complex 3 is a linear triple bridged (phenoxido and carboxylato) trinuclear Ni(II) complex. Variable-temperature magnetic susceptibility studies indicate the presence of ferromagnetic exchange coupling in complexes 1–3 with J values of 25.4, 28.1 and 6.2 cm–1 respectively. Theoretically obtained J values of 21.4 cm–1 (for 1), 22.0 cm–1 (for 2) and 9.3 cm–1 (for 3) corroborate very well the experimental results. DFT calculation also shows that stronger H-bonding interactions present in the case of carboxylate based coligands stabilise the triple oxido-bridged complexes. [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]

Bis-pyridazine tectons support the structure of metallosupramolecular cavitand Cu2L44+, which is capable of selective encapsulation of SiF62− anions by a set of multiple host–guest interactions. [ABSTRACT FROM AUTHOR]

A series of pyridinium-carboxylate salts (1–3) were designed, synthesized and structurally characterized to explore the importance of salt-bridge (SB) interactions in building self-assembled structures. We present a comprehensive analysis of the SB interaction in crystal structures of 4,4′-oxybis(benzoic acid) with substituted aminopyridines where the SBs display extremely well defined geometric preferences. In the solid-state, compound (1) exhibits lone-pair (l.p)⋯(SB)/(SB)⋯π+ assemblies while compound (2) shows a C–H⋯(SB)/(SB)⋯π network. Interestingly, compound (3) exhibits two distinct networks π+⋯(SB)/(SB)⋯(SB)/(SB)⋯π+ and C–H⋯(SB)/(SB)⋯H–C. These extended supramolecular networks are studied and described in detail. The duality of the SBs in stabilizing the π-facial interactions with electron rich and/or electron poor moieties is also described. The energetic and geometric features of salt-bridge interaction are studied and its impact on the resultant supramolecular organization is analyzed using theoretical DFT-D3 calculations. The theoretical study combines the energetic features of the noncovalent forces that participate in the extended network and the characterization of the diverse interactions by means of Bader's theory of 'atoms in molecules'(AIM). [ABSTRACT FROM AUTHOR]