Complex Salts of Lanthanide(III) Nitrates from Di­pyridylamine: Preparation,Structural, and Thermoanalytical ­Investigation

The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd) with the base 2, 2′‐dipyridylamine (dpamH) afforded two very stable microcrystalline compounds. These compounds were characterized as complex salts with the general formula [Ln(NO₃)₆] · 3[dpamH‐H⁺] · H₂O, where the dpamH ligand is not coordinated, but exists in its protonated form serving as counterion (dipyridylammonium cation), as it was revealed by single‐crystal X‐ray diffraction studies. Each one of the nitrate ions is coordinated, however, in a bidentate manner with the lanthanide(III) ion, which obtains coordination number twelve. All organic dpamH‐H⁺ cations are arranged in two columns parallel to the a axis of the cell forming pairs of almost parallel cationic molecules at a distance of about 3.5 Å. Inside each pair the molecules interact by strong π–π interactions. The water molecules, arranged between the inorganic anions [Ln(NO₃)₆]^3–, bridge them by strong hydrogen bonds, involving the water proton and one nitrate oxygen. The lattice can be described as made from successive organic and inorganic alternating parallel columns interacting between them with strong hydrogen bonds. The thermal stability and decomposition mode of the two lanthanide compounds were studied by the simultaneous TG/DTG‐DTA technique and compared with the starting hexahydrate lanthanide(III) salts and the dipyridylamine.     

Theoretical study on a chemosensor for fluoride anion‐based on a urea derivative

The sensing mechanism of the N‐Phenyl‐N′‐(3‐quinolinyl)urea (PQU) chemosensor for fluoride anion has been investigated by density functional theory/time‐dependent density function theory. The double intermolecular hydrogen bonds are formed between the three anions (X^??F^?, AcO^?, Cl^?) and the urea fragment of PQU. In the S₀ states, the H_b? X^? hydrogen bonds are slightly stronger than the H_a? X^? hydrogen bonds and the fluoride‐induced deprotonation occurs at the N? H_b position rather than at the N? H_a position. Consequently, the absorption peaks, including an intramolecular charge transfer transition and a ππ* transition, are significantly red‐shifted. Thermodynamic calculations confirm that the deprotonation in the ground state is favorable in energy only when excess fluoride anion exists. Along with the S₀ → S₁ transition, the H_a? X^? hydrogen bonds strengthen and the H_b? X^? hydrogen bonds weaken. However, the emission spectra of [PQU‐H_b]^?, instead of [PQU‐H_a]^?, are observed upon addition of fluoride anion. © 2013 Wiley Periodicals, Inc.     

Experimental and Computational Probes of the Nature of Halogen Bonding: Complexes of Bromine‐Containing Molecules with Bromide Anions

The nature of halogen bonding is examined via experimental and computational characterizations of a series of associates between electrophilic bromocarbons R? Br (R? Br=CBr₃F, CBr₃NO₂, CBr₃COCBr₃, CBr₃CONH₂, CBr₃CN, etc.) and bromide anions. The [R? Br, Br^?] complexes show intense absorption bands in the 200–350 nm range which follow the same Mulliken correlation as those observed for the charge‐transfer associates of bromide anions with common organic π‐acceptors. For a wide range of the associates, intermolecular R? Br???Br^? separations decrease and intramolecular C? Br bond lengths increase proportionally to the Br^?→R? Br charge transfer; and the energies of R? Br???Br^? bonds are correlated with the linear combination of orbital (charge‐transfer) and electrostatic interactions. On the whole, spectral, structural and thermodynamic characteristics of the [R? Br, Br^?] complexes indicate that besides electrostatics, the orbital (charge‐transfer) interactions play a vital role in the R? Br???Br^? halogen bonding. This indicates that in addition to controlling the geometries of supramolecular assemblies, halogen bonding leads to electronic coupling between interacting species, and thus affects reactivity of halogenated molecules, as well as conducting and magnetic properties of their solid‐state materials.     

Photomagnetic Switching of Heterometallic Complexes [M(dmf)4(H2O)3(μ‐CN)Fe(CN)5]⋅H2O (M=Nd,La, Gd,Y) Analyzed by Single‐Crystal X‐ray Diffraction and Ab Initio Theory

Single‐crystal X‐ray diffraction measurements have been carried out on [Nd(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 1 ; dmf=dimethylformamide), [Nd(dmf)₄(H₂O)₃(μ‐CN)Co(CN)₅]?H₂O ( 2 ), [La(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 3 ), [Gd(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 4 ), and [Y(dmf)₄(H₂O)₃(μ‐CN)Fe(CN)₅]?H₂O ( 5 ), at 15(2) K with and without UV illumination of the crystals. Significant changes in unit‐cell parameters were observed for all the iron‐containing complexes, whereas 2 showed no response to UV illumination. Photoexcited crystal structures have been determined for 1 , 3 , and 4 based on refinements of two‐conformer models, and excited‐state occupancies of 78.6(1), 84(6), and 86.6(7) % were reached, respectively. Significant bond‐length changes were observed for the Fe–ligand bonds (up to 0.19 Å), the cyano bonds (up to 0.09 Å), and the lanthanide–ligand bonds (up to 0.10 Å). Ab initio theoretical calculations were carried out for the experimental ground‐state geometry of 1 to understand the electronic structure changes upon UV illumination. The calculations suggest that UV illumination gives a charge transfer from the cyano groups on the iron atom to the lanthanide ion moiety, {Nd(dmf)₄(H₂O)₃}, with a distance of approximately 6 Å from the iron atom. The charge transfer is accompanied by a reorganization of the spin state on the {Fe(CN)₆} complex, and a change in geometry that produces a metastable charge‐transfer state with an increased number of unpaired electrons, thus accounting for the observed photomagnetic effect.     

4‐(3‐Azaniumylpropyl)morpholin‐4‐ium chloride hydrogen oxalate: an unusual example of a dication with different counter‐anions

The mixed organic–inorganic title salt, C₇H₁₈N₂O²⁺·C₂HO₄⁻·Cl⁻, forms an assembly of ionic components which are stabilized through a series of hydrogen bonds and charge‐assisted intermolecular interactions. The title assembly crystallizes in the monoclinic C2/c space group with Z = 8. The asymmetric unit consists of a 4‐(3‐azaniumylpropyl)morpholin‐4‐ium dication, a hydrogen oxalate counter‐anion and an inorganic chloride counter‐anion. The organic cations and anions are connected through a network of N—H...O, O—H...O and C—H...O hydrogen bonds, forming several intermolecular rings that can be described by the graph‐set notations R₃³(13), R₂¹(5), R₁²(5), R₂¹(6), R₂³(6), R₂²(8) and R₃³(9). The 4‐(3‐azaniumylpropyl)morpholin‐4‐ium dications are interconnected through N—H...O hydrogen bonds, forming C(9) chains that run diagonally along the ab face. Furthermore, the hydrogen oxalate anions are interconnected via O—H...O hydrogen bonds, forming head‐to‐tail C(5) chains along the crystallographic b axis. The two types of chains are linked through additional N—H...O and O—H...O hydrogen bonds, and the hydrogen oxalate chains are sandwiched by the 4‐(3‐azaniumylpropyl)morpholin‐4‐ium chains, forming organic layers that are separated by the chloride anions. Finally, the layered three‐dimensional structure is stabilized via intermolecular N—H...Cl and C—H...Cl interactions.     

Easily‐prepared Hydroxy‐containing Receptors Recognize Anions in Aqueous Media

Despite their ready availability, O?H groups have received relatively little attention as anion recognition motifs. Here, we report two simple hydroxy‐containing anion receptors that are prepared in two facile steps followed by anion exchange, without the need for chromatographic purification at any stage. These receptors contain a pyridinium bis(amide) motif as well as hydroxyphenyl groups, and bind mono‐ and divalent anions in 9:1 CD₃CN:D₂O, showing a selectivity preference for sulfate. Notably, a “model” receptor that does not contain hydroxy groups shows only very weak sulfate binding in this competitive solvent mixture. In the solid state, X‐ray crystallographic studies show that the receptors tend to form extended assemblies with anions; however, ¹H and DOSY NMR studies as well as molecular dynamics simulations show that only 1:1 complexes are present in solution. Molecular dynamics simulations suggest that one of the receptors suffers from competing intramolecular hydrogen bonding, while another binds partially‐hydrated anions, with the receptor's O?H groups forming hydrogen bonds to water molecules within the anion's coordination sphere.     

4‐Aminopyridinium 2‐(anthracen‐9‐yl)‐3‐oxo‐3H‐inden‐1‐olate monohydrate

The title compound, 2C₅H₇N₂⁺·2C₂₃H₁₃O₂⁻·H₂O, formed as a by‐product in the attempted synthesis of a nonlinear optical candidate molecule, contains two independent 4‐aminopyridinium cations and 2‐(anthracen‐9‐yl)‐3‐oxo‐3H‐inden‐1‐olate anions with one solvent water molecule. This is the first reported structure containing these anions. The two anions are not planar, having different interplanar angles between the anthracenyl and inden‐1‐olate moieties of 59.07 (5) and 83.92 (5)°. The crystal packing, which involves strong classical hydrogen bonds and one C—H...π interaction, appears to account for both the nonplanarity and this difference.     

Synthesis,Crystal Structures,and Photoluminescence of Lanthanide Coordination Polymers with 4‐Acetamidobenzoate

The reactions of Ln(NO₃)₃ · 6H₂O and 4‐acetamidobenzoic acid (Haba) with 4,4′‐bipyridine (4,4′‐bpy) in ethanol solution resulted in three new lanthanide coordination polymers, namely {[Ln(aba)₃(H₂O)₂] · 0.5(4,4′‐bpy) · 2H₂O}_∞ [Ln = Sm ( 1 ), Gd ( 2 ), and Er ( 3 ), aba = 4‐acetamidobenzoate]. Compounds 1 – 3 are isomorphous and have one‐dimensional chains bridged by four aba anions. 4,4′‐Bipyridine molecules don’t take part in the coordination with Ln^III ions and occur in the lattice as guest molecules. Moreover, the adjacent 1D chains in the complex are further linked through numerous N–H ··· O and O–H ··· O hydrogen bonds to form a 3D supramolecular network. In addition, complex 1 in the solid state shows characteristic emission in the visible region at room temperature.     

Cation–Cation Pairing by NCH⋅⋅⋅O Hydrogen Bonds

The pairing of ions of opposite charge is a fundamental principle in chemistry, and is widely applied in synthesis and catalysis. In contrast, cation–cation association remains an elusive concept, lacking in supporting experimental evidence. While studying the structure and properties of 4‐oxopiperidinium salts [OC₅H₈NH₂]X for a series of anions X^? of decreasing basicity, we observed a gradual self‐association of the cations, concluding in the formation of an isolated dicationic pair. In 4‐oxopiperidinium bis(trifluoromethylsulfonyl)amide, the cations are linked by N? H???O?C hydrogen bonds to form chains, flanked by hydrogen bonds to the anions. In the tetra(perfluoro‐tert‐butoxy)aluminate salt, the anions are fully separated from the cations, and the cations associate pairwise by N? C? H???O?C hydrogen bonds. The compounds represent the first genuine examples of self‐association of simple organic cations based merely on hydrogen bonding as evidenced by X‐ray structure analysis, and provide a paradigm for an extension of this class of compounds.     

[{Na(7‐Nitro‐5‐sulfonate‐naphthalene‐1,4‐dicarboxy‐acid (H2O)2}·H2O]n: A Water‐Soluble 2D Layer Polymeric Complex with Microporous Molecular Channels

The X‐ray crystallographic studies are reported for a water‐soluble sodium complex of organic acid, {[Na(NSNDC)(H₂O)₂]·H₂O}_n, (NSNDC = 7‐Nitro‐5‐sulfonate‐napthalene‐1,4‐dicarboxy‐acid). It contains layers of vertically oriented NNSDC‐anions sandwiching cations and water molecules. The rows of anions are linked in a direction by sodium ions and along b by hydrogen bonding, which have microporous channels (9.410 × 3.210Ų) along the crystallographic b‐axis. Considering the Na coordination environments, π‐π stacking interaction between aryl ring and hydrogen bonds, the title compound represents a stably 2D infinitely extended structure.     

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy,X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Ten [C₈C₁Im]⁺ (1‐methyl‐3‐octylimidazolium)‐based ionic liquids with anions Cl^?, Br^?, I^?, [NO₃]^?, [BF₄]^?, [TfO]^?, [PF₆]^?, [Tf₂N]^?, [Pf₂N]^?, and [FAP]^? (TfO=trifluoromethylsulfonate, Tf₂N=bis(trifluoromethylsulfonyl)imide, Pf₂N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C₈C₁C₁Im]⁺ (1,2‐dimethyl‐3‐octylimidazolium)‐based ionic liquids with anions Br^? and [Tf₂N]^? were investigated by using X‐ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While ¹H NMR spectroscopy is found to probe very specifically the strongest hydrogen‐bond interaction between the hydrogen attached to the C² position and the anion, a comparative XPS study provides first direct experimental evidence for cation–anion charge‐transfer phenomena in ionic liquids as a function of the ionic liquid’s anion. These charge‐transfer effects are found to be surprisingly similar for [C₈C₁Im]⁺ and [C₈C₁C₁Im]⁺ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.     

Carboxylate–phenolate tautomerism in 5‐[(nitrophenyl)diazenyl]salicylate anions

Aryldiazenyl derivatives of salicylic acid and their salts are used as dyes. In these structures, the carboxylate groups are engaged in short contacts with the cations and in hydrogen bonds with water molecules, if present. If both O atoms of the carboxylate group take part in such interactions, the negative charge is delocalized over the two atoms. In the absence of hydrogen bonds and contacts with cations, the negative charge is localized on one of the O atoms. In the crystal structures of tetramethylammonium 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoate and tetramethylammonium 2‐hydroxy‐5‐[(E)‐(2‐nitrophenyl)diazenyl]benzoate, both C₄H₁₂N⁺·C₁₃H₈N₃O₅⁻, all the interactions between the cations and anions are weak, and their effect on the geometry of the anions is negligible. Under these conditions, the 2‐nitro‐substituted anion is an almost pure phenol–carboxylate tautomer, whereas in the 4‐nitro‐substituted anion, the phenolic H atom is shifted towards the carboxylate group, and thus the structure of this anion is intermediate between the phenol–carboxylate and phenolate–carboxylic acid tautomeric forms. The probable formation of such an intermediate form is supported by quantum chemical calculations. Being the characteristic feature of this form, a short distance between the phenolic and carboxylate O atoms is observed in the 4‐nitro‐substituted anion, as well as in the structures of some 3,5‐dinitrosalicylates reported in the literature.     

A Novel Organosulfonate Cadmium(II) Complex with Graphite‐like 2D Layer Linked by Hydrogen Bonds

A novel mixed‐ligand complex, [Cd(im)₆][Cd(im)₃(H₂O)₃]₂(ans)₆ · 8H₂O ( 1 ), was obtained from the reaction ofCd(OAc)₂ · 2H₂O, imidazole (im) and sodium 4‐aminonaphthalene‐1‐sulfonate tetrahydrate (Na‐ans) in a mixed solvent at 25 °C. The complex was characterized by elemental analysis, IR spectroscopy, and X‐ray single crystal diffraction. There are two kinds of cations constructed by Cd^II atoms with a octahedral coordination arrangement in 1 . The Cd^II atom is bonded by six nitrogen atoms from six im ligands in the first cation, and the second central Cd^II atom is bonded by three nitrogen atoms of im molecules and three oxygen atoms belonging to water molecules. The ans anion acts as a counterion to balance the charge, and the adjacent anions are reversed but non‐parallel interlinked by N–H ··· O(S) hydrogen bonds into graphite‐like 2D sheet viewed from the c axis. The anionic channels along the [110] direction are filled with the cations, and the two kinds of cations are alternatingly arranged in the channels. The hydrogen‐bonding interactions together with the ionic bonds stabilize the crystal structure. The thermostability of the complex was investigated by TG and DSC.     

Theoretical Study on Hydrogen Bonding of Mono‐ and Dihydrated Complexes of 7‐(3′‐Pyridyl)indole in Excited States

The intermolecular hydrogen bonds of mono‐ and dihydrated complexes of 7‐(3′‐Pyridyl)indole (7‐3′PI) have been investigated using the time‐dependent density functional theory (TD‐DFT) method. The electrostatic potential analysis of monomer 7‐3′PI and 7‐(3′‐Pyridyl)indole‐water (7‐3′PI‐W) indicates that an intermolecular hydrogen bond between two waters can be formed for 7‐(3′‐Pyridyl)indole‐2water (7‐3′PI‐2W) complex. The calculated bond lengths of the intermolecular hydrogen bonds of 7‐3′PI‐W and 7‐3′PI‐2W in the S₁ state (the first excited singlet state) are all shortened compared to the ground state. By the analysis of bond length, charge population and infrared spectra, it is demonstrated that the intermolecular hydrogen bonds of 7‐3′PI‐W and 7‐3′PI‐2W are all strengthened upon electronic excitation to the S1 state. Moreover, the fluorescence of 7‐3′PI‐W and 7‐3′PI‐2W are all red‐shifted to larger wavelength compared to monomer 7‐3′PI. The red‐shift of fluorescence peak of 7‐3′PI‐W and 7‐3′PI‐2W should be attributed to the change of hydrogen bond interaction before and after photoexcitation. Therefore, it can be concluded that the intermolecular hydrogen bonding strengthening in the excited S₁ state induces the fluorescence weakening of 7‐3′PI.     

The investigation of proton transfer and fluorescence‐sensing mechanisms of [2‐(2‐hydroxy‐phenyl)‐1H‐benzoimidazol‐5‐yl]‐phenyl‐methanone

Given the tremendous potential of fluorescence sensors in recent years, in this present work, we theoretically explore a novel fluorescence chemosensor [2‐(2‐Hydroxy‐phenyl)‐1H‐benzoimidazol‐5‐yl]‐phenyl‐methanone (HBPM) about its excited state behaviors and probe‐response mechanism. Using density functional theory (DFT) and time‐dependent density functional theory (TDDFT) methods, we explore the S₀‐state and S₁‐state hydrogen bond dynamical behaviors and confirm that the strengthening intramolecular hydrogen bond in the S₁ state may promote the excited state intramolecular proton transfer (ESIPT) reaction. In view of the photoexcitation process, we find that the charge redistribution around the hydroxyl moiety plays important roles in providing driving force for ESIPT. And the constructed potential energy curves further verify that the ESIPT process of HBPM should be ultrafast. That is the reason why the normal HBPM fluorescence cannot be detected in previous experiment. Furthermore, with the addition of fluoride anions, the exothermal deprotonation process occurs spontaneously along with the intermolecular hydrogen bond O–H?F. It reveals the uniqueness of detecting fluoride anions using HBPM molecules. As a whole, the fluoride anions inhibit the initial ESIPT process of HBPM, which results in different fluorescence behaviors. This work presents the clear ESIPT process and fluoride anion‐sensing mechanism of a novel HBPM chemosensor.     

Codeine dihydrogen phosphate hemihydrate

The cation of the title structure [systematic name: (5α,6α)‐6‐hydroxy‐7,8‐didehydro‐4,5‐epoxy‐3‐methoxy‐17‐methylmorphinanium dihydrogen phosphate hemihydrate], C₁₈H₂₂NO₃⁺·H₂PO₄⁻·0.5H₂O, has a T‐shaped conformation. The dihydrogen phosphate anions are linked by O—H...O hydrogen bonds to give an extended ribbon chain. The codeine cations are linked together by O—H...O hydrogen bonds into a zigzag chain. There are also N—H...O bonds between the two types of hydrogen‐bonded units. Addditionally, they are connected to one another via O...H—O—H...O bridging water molecules. The asymmetric unit contains two codeine hydrogen cations, two dihydrogen phosphate anions and one water molecule. This study shows that the water molecules are firmly bound within a complex three‐dimensional hydrogen‐bonded framework.     

New insights into water‐soluble and water‐coordinated copper 15‐metallacrown‐5 gadolinium complexes designed for high‐field magnetic resonance imaging applications

The development of contrast agents specifically designed for high‐field magnetic resonance imaging (MRI) is required because the relaxation efficiency of classic Gd(III) contrast agents significantly decreases with increasing magnetic field strengths. With an idea of exploring the unique structure of lanthanide (Ln) 15‐MC‐5 metallacrowns, we developed a series of water‐soluble Gd(III) aqua‐complexes, bearing aminohydroxamate (glycine, α‐alanine, α‐phenylalanine and α‐tyrosine) ligands, with increasing number of water molecules directly coordinated to the Gd(III) ion: Gd(H₂O)₄[15‐MC_Cu(II)Glyha‐5](Cl)₃ ( 1 (Gd)), Gd(H₂O)₄[15‐MC_Cu(II)Alaha‐5](Cl)₃ ( 2 (Gd)), Gd(H₂O)₃[15‐MC_{Cu(II)Phalaha}‐5](Cl)₃ ( 3 (Gd)) and Gd(H₂O)₃[15‐MC_Cu(II)Tyrha‐5](Cl)₃ ( 4 (Gd)). In these systems, the Ln(III) central ion is coordinated by five oxygen donor atoms of the ligands and three or four inner‐sphere water molecules. The X‐ray crystal structure of metallacrown Ln(H₂O)_3,4[15‐MC_Cu(II)Rha‐5]³⁺ agrees with density functional theory predictions. The calculations demonstrate that the exchange of coordinated water molecules can proceed easily, resulting in increased relaxivity parameters. The longitudinal relaxivities (r₁) of 1 (Gd)– 4 (Gd) in water at ultrahigh magnetic field of 9.4 T were determined to be 11.5, 14.8, 13.9 and 12.2 mM^?1 s^?1, respectively. The ability to increase the number of Ln(III) inner‐sphere water molecules up to four, the planar metallacrown structure and the rich hydration shell due to strong hydrogen bonds between the [15‐MC‐5] moiety and bulk water molecules provide new opportunities for potential MRI applications.     

Synthesis and X‐ray Crystallography of Two Lead(II) Decahydro‐closo‐Decaborate Hydrates

The reaction of Pb[CO₃] with an aqueous solution of (H₃O)₂[B₁₀H₁₀] in an equimolar ratio leads to two lead(II) decahydro‐closo‐decaborate hydrates both as triclinic, pale yellow single crystals. The water‐rich compound with the formula [Pb(H₂O)₃]₂Pb[B₁₀H₁₀]₃ · 5.5H₂O crystallizes in the space group P1 (a = 711.72(4), b = 1243.14(8), c = 2064.83(12) pm, α = 81.806(3), β = 83.795(3), γ = 80.909(3)°) with Z = 2. The compound with the lower water content, [Pb(H₂O)₃]Pb[B₁₀H₁₀]₂ · 1.5H₂O, also crystallizes in P1 (a = 718.46(4), b = 1288.75(8), c = 1279.91(8) pm, α = 70.145(3), β = 75.976(3), γ = 80.324(3)°) with Z = 2. Both structures can be described as layered arrangements and contain one Pb²⁺ cation each, which is only coordinated by the hydridic hydrogen atoms of the hydroborate anions. All the others are primarily surrounded by three water molecules in a non‐planar fashion and additional hydrogen atoms of [B₁₀H₁₀]^2– anions. The non‐lead‐bonded crystal water molecules in both structures are all connected via hydrogen bonds to the water molecules, which coordinate the Pb²⁺ cations, as well as via non‐classical hydrogen bonds to the cluster anions and reside between the layers. The [B₁₀H₁₀]^2– anions show only slight distortions from their ideal shape as bicapped square antiprisms.     

4-羟甲基吡啶－水红移氢键的密度泛函理论研究

使用密度泛函理论B3LYP方法和6-311++G**基函数对4-羟甲基吡啶与水形成的1:1和1:2（摩尔比）氢键复合物进行了理论计算研究,分别得到稳定的4-羟甲基吡啶－H₂O和4-羟甲基吡啶－(H₂O)₂氢键复合物3个和8个。经基组重叠误差和零点振动能校正后,最稳定的1:1和1:2氢键复合物的相互作用能分别为-20.536和-44.246 kJ/mol。振动分析显示O-H···N(O)氢键的形成使复合物中O-H键对称伸缩振动频率红移(减小)。自然键轨道分析表明,4-羟甲基吡啶与水形成最稳定的1:1和1:2氢键复合物时,分子间电荷转移分别为0.02642 e 和0.03813 e 。含时密度泛函理论TD-B3LYP/ 6-311++G**计算显示,相对于4-羟甲基吡啶单体分子,氢键H-OH···N和H-OH···OH的形成分别使最大吸收光谱波长兰移8~16纳米和红移4~11纳米。     

Protonated Melonate Ca[HC6N7(NCN)3]·7H2O – Synthesis,Crystal Structure,and Thermal Properties

Calcium hydrogenmelonate heptahydrate Ca[HC₆N₇(NCN)₃] · 7H₂O was obtained by metathesis reaction in aqueous solution. The structure of the molecular salt was elucidated by single‐crystal X‐ray diffraction. The crystal structure consists of alternating layers of planar monopronated melonate ions, Ca²⁺ and crystal water molecules. The anions of adjacent layers are staggered so that no π–π stacking occurs. The melonate entities are interconnected by hydrogen bonds within and between the layers. Ca[HC₆N₇(NCN)₃] · 7H₂O was investigated by solid‐state NMR and FTIR spectroscopy, TG and DTA measurements.