Multiresponsive supramolecular gels constructed by orthogonal metal–ligand coordination and hydrogen bonding

Macromonomers bearing tridentate 2,6-bis(1,2,3-trizol-4-yl)pyridine (BTP) ligand unit synthesized via CuAAC “click” chemistry in the middle of the chain and two ureidopyrimidinone (UPy) motifs on the ends linked to the central BTP unit via PEGs of various lengths were synthesized and used for the study of gelation both with and without the presence of Eu(III) ions. Various interesting gelation behaviors were found. Gels exhibited various multi-responsive properties, including photoluminescence, mechanoresponsive properties, self-healing abilities, thermorepsonsive properties and chemoresponsive properties. The different gelation abilities and multi-responsive properties for different systems were shown to be resulted from difference in PEG linker lengths and the introduction of orthogonal metal–ligand coordination and hydrogen bonding interactions. The selective responsiveness to different chemicals would allow the development of modular sensory systems that utilize a combination of orthogonal supramolecular interactions.     

Supramolecular structures of CdX2-containing coordination compounds constructed by C–H ··· X synthons

Three CdX₂-containing (X = Cl, Br) compounds [CdBr₂(Him)₂] _n (Him = imidazole) (1), [CdCl₂(2,2′-bipy)] _n (2,2′-bipy = 2,2′-bipyridine) (2), and [CdCl₂(phen)] (phen = phenanthroline) (3) have been synthesized through hydrothermal technique. Compound 1 adopts 1-D coordination chain, which is connected to form a 3-D supramolecular network by inter-chain N–H ··· Br and C–H ··· Br hydrogen bonds. Compound 2 also adopts 1-D coordination chain, which is connected to form 3-D supramolecular network by intra- and inter-chain C–H ··· Cl hydrogen bonds; 3 is discrete, linked to form 2-D supramolecular sheets by intra- and inter-molecular C–H ··· Cl hydrogen bonds. The different volume and coordination ability of organic ligands result in the different coordination structure and supramolecular synthons. All these compounds exhibit strong fluorescence emissions at room temperature.     

Assessment of intermolecular N–H…F and N–H…Cl hydrogen bonding in stabilising hetero- and homodimers in solution

This paper describes the first assessment of intermolecular weak N–H…F and N–H…Cl hydrogen bonding in stabilising hetero- and homodimers in solution. Aromatic amide and urea monomers have been designed and synthesised. The association constants of the heterodimers formed by two complementary monomers and the homodimers formed by self-complementary monomers have been determined by using ¹H titration and dilution experiments. The results show that both N–H…F and N–H…Cl hydrogen bonds are able to stabilise the corresponding dimers to a measurable extent, even though the stability of the dimers is generally low.     

N,N′-methylenedipyridinium Pt(II) and Pt(IV) hybrid salts: synthesis, crystal and molecular structures of [(C5H5N)2CH2] · [PtCl4] and [(C5H5N)2CH2] · [PtCl6]

The highly insoluble organic-inorganic hybrid ionic compounds N,N??-methylenedipyridinium tetrachloroplatinate(II) [(C₅H₅N)₂CH₂] · [PtCl₄] and N,N??-methylenedipyridinium hexachloroplatinate(IV) [(C₅H₅N)₂CH₂] · [PtCl₆] were obtained by the treatment of N,N??-methylenedipyridinium dichloride monohydrate [(C₅H₅N)₂CH₂]Cl₂ · H₂O with K₂[PtCl₄] or (NH₄)₂[PtCl₆], respectively, in an aqueous solution. Both complexes were isolated, purified, characterised by elemental analysis, and their molecular structures were confirmed by powder X-ray diffraction. The crystal structure of both compounds consists of separated discrete dications [(C₅H₅N)₂CH₂]²⁺ and anions [PtCl _n ]^2? (n = 4 or 6). As anticipated, the dications formed a butterfly shape consisting of two pyridine rings bound to the methylene group via their N atoms, while the Pt centre had a square planar geometry in [(C₅H₅N)₂CH₂] · [PtCl₄] and an octahedral coordination in [(C₅H₅N)₂CH₂] · [PtCl₆]. Interestingly, both crystal structures are stabilised by intermolecular C-H??Cl non-standard hydrogen bonds, ??-?? ring interactions between two pyridine rings of adjacent dications, and also by Cl-?? interactions.     

N-H…X (X = F, Cl, Br, and I) hydrogen bonding in aromatic amide derivatives in crystal structures

Intramolecular N H···X (X=F, Cl, Br, and Ⅰ) hydrogen bonding patterns of aromatic amides in the solid state are summarized. It is revealed that the key for the formation of this kind of weak intramolecular hydrogen bonding in X-ray crystal structures is to suppress the competition of strong intermolecular N H···O C hydrogen bonding of the amide unit. For amides with identical backbones, the bonding capacity of halogen atoms as hydrogen bonding acceptors is in the order of F>Cl>Br>I, which is in accordance with their electronegativity strength. Generally, the five-membered hydrogen bonding is easier to form than the six-membered one.     

Theoretical study of N–H· · ·O hydrogen bonding properties and cooperativity effects in linear acetamide clusters

We investigated geometry, energy, ${\nu_{{\text{N--H}}}}$ harmonic frequencies, ¹⁴N nuclear quadrupole coupling tensors, and ${n_{\rm O}\to \sigma _{{\text{N--H}}}^\ast}$ charge transfer properties of (acetamide) _n clusters, with n = 1 ? 7, by means of second-order Møller-Plesset perturbation theory (MP2) and DFT method. Dependency of dimer stabilization energies and equilibrium geometries on various levels of theory was examined. B3LYP/6-311++G** calculations revealed that for acetamide clusters, the average hydrogen-bonding energy per monomer increases from ?26.85 kJ mol^?1 in dimer to ?35.12 kJ mol^?1 in heptamer; i.e., 31% cooperativity enhancement. The n-dependent trend of ${\nu_{{\text{N--H}}}\,{and}\,^{14}}$ N nuclear quadrupole coupling values were reasonably correlated with cooperative effects in ${r_{{\text{N--H}}}}$ bond distance. It was also found that intermolecular ${n_{\rm O}\to \sigma_{{\text{N--H}}}^\ast}$ charge transfer plays a key role in cooperative changes of geometry, binding energy, ${\nu_{{\text{N--H}}}}$ harmonic frequencies, and ¹⁴N electric field gradient tensors of acetamide clusters. There is a good linear correlation between ¹⁴N quadrupole coupling constants, C _Q (¹⁴N), and the strength of Fock matrix elements (F _ij ). Regarding the ${n_{\rm O}\to \sigma_{{\text{N--H}}}^\ast}$ interaction, the capability of the acetamide clusters for electron localization, at the N–H· · ·O bond critical point, depends on the cluster size and thereby leads to cooperative changes in the N–H· · ·O length and strength, N–H stretching frequencies, and ¹⁴N quadrupole coupling tensors.     

Morpholine adducts of Co, Ni, and Mn benzoylacetonates: isostructurality and C–H···O hydrogen bonding

Morpholine adducts of nickel(II), cobalt(II), and manganese(II) benzoylacetonates, as well as a morpholine solvate of manganese(II) benzoylacetonate, were prepared and characterized by X-ray diffraction and thermal analysis. All four compounds crystallize in the P2₁/c space group with two complex molecules per unit cell. The morpholine solvate, along with the two adduct molecules, also contains four solvent morpholine molecules in the unit cell. The non-solvate compounds are isostructural, with crystal structures comprising 2D networks formed by C–H···O hydrogen bonding between phenyl rings and morpholine oxygen atoms. The topology of these networks can be described as intersecting C₂²(24) chains forming R₄⁴(48) rings. Networks with the same topology are also present in the solvate, but they are heavily distorted due to the presence of solvent morpholine molecules. Thermogravimetric analysis shows similar behavior of the non-solvate compounds upon thermal decomposition, with three degradation steps which can be related to gradual loss of morpholine molecules and subsequent overall decomposition. Decomposition of the solvate also proceeds in several steps, the first of which can be related to loss of solvent morpholine molecules and the further steps are analogous to those in the non-solvate compounds.     

Phase transitions in (C7H12N2)2[SnCl6]Cl2·1.5H2O crystal,studied by NMR and infrared spectroscopy

The (C₇H₁₂N₂)₂[SnCl₆]Cl₂·1.5H₂O complex is a new member of the family of hybrid organic–inorganic perovskite compounds. It exhibits two order–disorder phase transitions with changes in the conformation of aromatic cations at the two transition temperatures 360 and 412 K. Differential scanning calorimetry, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FT-IR) spectroscopy were used to investigate these phase transitions. These transition mechanisms were investigated in terms of the spin–lattice relaxation times T1 for ¹H static NMR and the chemical shifts for ¹³C CP–MAS. The temperature dependence of T1(¹H) and ¹³C chemical shifts are changed near T_C1 and T_C2. Furthermore, the splitting for ¹³C NMR signals in Phases (II) and (III) indicated a ferroelastic characteristic of the compound. In addition, FT-IR results indicate that the ordered conformational structure of aromatic cations undergoes a remarkable disorder with increasing temperature. The NMR and FT-IR studies suggest that the phase transition mechanisms are related to the reorientational motion of [C₇H₁₂N₂]²⁺ cations as a whole. Phase transition was examined in light of the interesting optical properties of this material.     

X-ray crystal structure,spectral and magnetic properties of end-to-end di-μ-thiocyanatobis(imidazole)M(II) polymeric complexes (M=Co,Mn): supramolecular network structure based on N–H ··· S hydrogen bonding and π ··· π stacking

Two isomorphous one-dimensional chain complexes Co(NCS)₂(Him)₂ (1) and Mn(NCS)₂(Him)₂ (2) (Him?=?imidazole) have been prepared and characterized structurally. Both 1 and 2 crystallize in the monoclinic system, space group P2₁/n, and the structures consist of one-dimensional polymeric chains in which metal ions are bridged by two thiocyanate groups bonding in end-to-end fashion. Both 1 and 2 exhibit two-dimensional sheet structures with N–H?···?S hydrogen bonds and three-dimensional supramolecular network structure with π?···?π stacking interactions. IR spectra indicate the presence of bridging thiocyanate groups in both 1 and 2, confirmed by their structures. The variable temperature magnetic susceptibility, measured in the 2–300?K range, indicates weak antiferromagnetic exchange interactions in complex 2.     

Hydrothermal synthesis,crystal structures,and blue photoluminescence of two 2-D Ag–1,2,4-triazolate coordination polymers with 4462 topology

Two 2-D metal-organic coordination polymers, {[Ag(NH₂–BPT)] · NO₃} _n (1) and {[Ag(BPT)] · H₂O} _n (2), have been synthesized via self-assembly of AgNO₃ and 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole (NH₂–BPT) under hydrothermal conditions by controlling the reaction temperatures. Lower reaction temperature (140°C) led to formation of 1, which crystallizes in the monoclinic system, space group C2/c, a = 24.001(3), b = 15.844(2), and c = 12.981(3) Å, V = 2996.8(6) ų, Z = 8. When the temperature was increased to 180°C, in situ deaminization of the organic ligand led to crystallization of 2 (space group P₂1 /n, a = 7.3106(10), b = 19.633(2), and c = 9.0596(16) Å, V = 1190.2(3) ų, Z = 4). The NH₂–BPT in 1 and BPT in 2 are μ₄ tetradentate utilizing two triazolyl and two pyridyl nitrogens, generating an unusual 2-D layer, in which binuclear Ag(I) motifs and organic ligands are four-connecting nodes that inter-link in 4⁴6² topology. Adjacent 2-D metal-organic layers are linked by a system of hydrogen bonds to form 3-D supramolecular frameworks. Strong blue fluorescence emissions are observed for 1 and 2 in the solid state at ambient temperature.     

Syntheses and structures of M–Na (M=Zn,Mn) coordination polymers in which ligands and Na ions exhibit complex coordination modes

The novel heteronuclear complexes [Na₂Zn(dipic)₂(H₂O)] _n (1) and [Na₂Mn(dipic)₂(H₂O)₂] _n (2) (H₂dipic?=?pyridine-2,6-dicarboxylic acid) were synthesized and characterized by single-crystal X-ray diffraction, analysis, IR spectroscopy and thermogravimetric analysis. Complex 1 consists of infinite 2D double layers, which are further attached into a 3D network through π–π stacking. All sodium ions are 3-coordinate. Complex 2 has an intricate 3D structure, in which two sodium ions are differently involved in forming polymeric coordination units, and are 3- and 7-coordinate, respectively. Dipic anions act as multidentate ligands showing novel and unprecedented bridging coordination modes. One ligand coordinates to three metal ions and with five bonds; the other coordinates five metal ions with nine bonds.     

A 3D interpenetrating supramolecular compound based on Cu ··· N weak coordination: synthesis,crystal structure and DFT investigation

A metal-organic hybrid compound, Cu[(pyc)₂(4,4′-bipy)] ·?H₂O (pyc =?pyridine-2-carboxylate, 4,4′-bipy =?4,4′-bipyridine), has been hydrothermally synthesized and characterized by X-ray determination, IR and elemental analysis. The compound crystallizes in tetragonal, space group I4₁/acd with a =?24.797(2) Å, b =?24.797(2) Å, c =?14.811(2) Å, β =?90°, V =?9106.7(18) ų, C₂₂ H₁₈N₄O₅Cu, Mr =?481.94, Dc =?1.406 g cm^?3, μ(Mo-Kα) =?0.999 mm^?3, F(000) =?3952, Z =?16, the final R =?0.0712 and wR =?0.1886 for 21727 observed reflections (I >?2σ). Compound 1 exhibits a three-dimensional interpenetrating network induced by weak Cu ··· N noncovalent interaction, C–H ··· π?and π–π interactions. Based on crystal data, quantum chemistry calculation at the DFT/B3LPY level was used to reveal the electronic structure of 1.     

Copper(I) halide complexes with a sterically hindered thiourea: synthesis and crystal structures of [Cu(dchtu)2Cl] and [Cu(dchtu)2Br] (dchtu = N,N ′-dicyclohexylthiourea)

Copper(I) complexes with a sterically hindered thiourea, [Cu(dchtu)₂X] (dchtu = N,N′-dicyclohexylthiourea; X=Cl 1, Br 2), were synthesized and their crystal structures were determined. Compounds 1 and 2 are isostructural orthorhombic, space group P2₁2₁2₁. Crystallographic data for 1 : a = 13.1711(13), b = 14.2610(19), c = 15.793(2) Å, V = 2966.4(6) ų, Z = 4. For 2 : a = 13.2628(13), b = 14.3410(19), c = 15.860(2) Å, V = 3016.5(6) ų, Z = 4. The stoichiometry of CuX complexes with thiourea is influenced by substituents on the nitrogens. Copper(I) halides only form bis-adducts with the sterically hindered dchtu ligand even with molar excesses of dchtu due to steric hinderance of the cyclohexyl substituents. In 1 and 2, the Cu(I) is trigonally coordinated by the sulfur atoms of two monodentate N,N′-dicyclohexylthiourea ligands and one halide. The structures of the complexes are stabilized by a system of intermolecular H-bonding.     

Three-dimensional 3d–4f hetero-bimetallic coordination polymers through hydrogen bonds: synthesis,structures and mössbauer spectrum analysis

Four cyano-bridged 3d–4f hetero-bimetallic Ln(III)–Fe(III) assemblies, {[Ln(DMF)₄(H₂O)₃(µ-CN)Fe(CN)₅]· H₂O} _n (Ln?=?Ce (1), Nd (2), Sm (3) and Gd (4); DMF?=?N,N-dimethylformamide), have been synthesized. X-ray crystallographic analysis of both 3 and 4 reveals three-dimensional network structures resulting from hydrogen bonds in the crystals. With respect to the coordination number on Sm(III) atoms, 3 is different from previously reported structures. Structural comparison indicates that the differences in magnetic properties between 3 and 4 do not derive from structural factors. Mössbauer spectra at both 298 and 10?K reveal that the characteristic quadrupole splitting for low-spin Fe(III) ions (S?=?1/2) remains unchanged, indicating that the spin state of Fe(III) ions in 1–4 is not affected by temperature. The magnetic anisotropy derived from the ground states of Ln(III) ions with odd 4f ⁿ electrons (n?=?1, 3, 5 and 7), ²F_5/2,⁴I_9/2, ⁶H_5/2 and ⁸S_7/2 for Ce(III), Nd(III), Sm(III) and Gd(III), respectively, dominates the exchange interaction in the Ln(III)–NC–Fe(III) systems.     

Novel inorganic ionic compounds based on Re6 chalcocyanide cluster complexes: synthesis and crystal structures of [CuNH3(trien)]2[Re6S8(CN)6] · 7H2O, [CuNH3(trien)]2[Re6Se8(CN)6] and [CuNH3(trien)]2[Re6Te8(CN)6] · H2O

Three new octahedral rhenium chalcocyanide cluster compounds [CuNH₃(trien)]₂[Re₆S₈(CN)₆] · 7H₂O (1), [CuNH₃(trien)]₂[Re₆Se₈(CN)₆] (2) and [CuNH₃(trien)]₂[Re₆Te₈(CN)₆] · H₂O (3) exhibiting ionic structures have been obtained by the diffusion of an ammonia solution of KCs₃[Re₆S₈(CN)₆] (for 1), K₄[Re₆Se₈(CN)₆] · 3.5H₂O (for 2) or Cs₄[Re₆Te₈(CN)₆] · 2H₂O (for 3) into a glycerol solution of CuCl₂ · 2H₂O in the presence of trien (trien=triethylenetetramine). The compounds have been characterized by single-crystal X-ray diffraction. All three compounds contain a cationic complex [CuNH₃(trien)]²⁺ which was not described previously.     

Synthesis of novel O-alkylbenzochromeno-1,5-benzodiazepinones. Study of the N–H····N and CO····HN hydrogen bonding interactions with 2-aminopyridines

A series of novel 6-(O-alky)lbenzochromeno-1,5-benzodiazepin-2-ones 4a–c was prepared through the condensation between the [1]benzopyrano[4,3-c][1,5]benzodiazepin-7(8H)one 1 and a series of alkylalcohols. Scaffold 4 exhibited interesting hydrogen-bonding interaction with 2-aminopyridine derivatives. The so obtained self-assembled systems 5 were fully characterized by 1D/2D-NMR techniques and mass spectrometry. The hydrogen-bonding interaction was supported by IR and Raman spectroscopy and by ¹H NMR titration experiments, and was confirmed by an X-ray crystal structure analysis.     

Theoretical Studies on the M-M Bonding in Complexes [M2Cl4L2] and [M2Cl7L]- （M = Mo, Re; L = Ph2Ppy, （Ph2P）2py）

The structures of complexes [MⅡ2Cl4L2] and [MⅢ2Cl7L]- (M = Mo, Re; L = Ph2Ppy, (Ph2P)2py) were calculated by using density functional theory (DFT) PBE0 method. Based on the optimized geometries, the natural bond orbital (NBO) analyses were carried out to study the nature of Re-Re and Mo-Mo bonds. The conclusions are as follows: the M-M distances in two-Ph2Ppy or (Ph2P)2py complexes [MⅡ2Cl4L2] are shorter than those in mono-Ph2Ppy or (Ph2P)2py complexes [MⅢ2Cl7L]- due to the double bridged N-C-P interactions. For singlet of all complexes, there is ReⅢ-ReⅢ or MoⅡ-MoⅡ quadruply bond in complex [Re2Cl7L]- or [Mo2Cl4L2], while only ReⅡ-ReⅡ or MoⅢ-MoⅢ triply bond in complex [Re2Cl4L2] or [Mo2Cl7L]-. The most stable spin state of 2 and 6, triplet, only contains triple ReⅢ-ReⅢ bond. Because the LPCl → BD*Re-Re delocalizations weaken the Re-Re bond, the distance of ReⅢ-ReⅢ quadruple bonds in [Re2Cl7L]- is slightly longer than that of ReⅡ-ReⅡ triple bonds in [Re2Cl4L2]. Moreover, due to the delocalizations from the lone pair electrons of the remaining P' atom to the M-M antibonding orbitals, the M-M distance in (Ph2P)2py complexes is slightly longer than that in Ph2Ppy complexes.     

Platinum precursor of anticancer drug: a structure fixed by long intermolecular N–H···I and C–H···I hydrogen bonds

The title compound 1, cis-[diiodo(1R,2R)-1,2-diaminocyclohexane-κN,κN′]platinum(II), a precursor of a novel platinum-based anticancer complex, was synthesized. High purity (>99%) was determined by HPLC–UV/VIS and its structure was characterized by LC–ESI–MS, FT-IR and X-ray single-crystal diffraction. The molecules of the title compound interact via N–H···I and C–H···I intermolecular (ultra)-long hydrogen–iodine (acceptor) bonds (distances up to 3.1 Å). The crystal structure of the title compound 1 was compared to the structure calculated on the basis of density function theory (DFT). The calculated and measured data varied by a maximum of 0.09 Å in bond lengths and the maximum deviation between the compared angles were less than 2°. Experimentally measured bond lengths in the crystal were observed to be reduced when compared to the theoretical calculation. This was caused by both steric requirements of individual structural units and the presence of hydrogen bonds in real sample, which were confirmed by FT-IR (new bands as well as the band shifts to lower wavelengths).