2-Amino­anilinium 2-chloro­acetate

In the crystal structure of the title compound, C6H9N2 +·ClCH2COO−, prepared by the reaction of OPDA (orthophenelynediamine) with chloro­acetic ­acid, N—H⋯O hydrogen bonds generate ladder-like chains and very weak inter­molecular C—H⋯Cl hydrogen-bonding inter­actions between the anions and cations lead to a supra­molecular network. C—H⋯O inter­actions also occur

Diversities of Coordination Geometry Around the Cu²⁺ Center in Bis(maleonitriledithiolato)metalate Complex Anions: Geometry Controlled by Varying the Alkyl Chain Length of Imidazolium Cations

Six new ion-pair metal-bis­(dithiolene) complexes with the formulas [C₉H₁₄N₄]­[Cu­(mnt)₂] <b>(1a</b>), [C₁₀H₁₆N₄]­[Cu­(mnt)₂] (<b>1b</b>), [C₁₁H₁₈N₄]­[Cu­(mnt)₂] (<b>1c</b>), [C₁₂H₂₀N₄]­[Cu­(mnt)₂] (<b>1d</b>), [C₁₃H₂₂N₄]­[Cu­(mnt)₂] (<b>1e</b>), and [C₁₄H₂₄N₄]­[Cu­(mnt)₂] (<b>1f</b>) have been synthesized starting from Cu­(II) salt, Na₂mnt (disodium maleonitriledithiolate), and bromide salts of alkyl-bis­(imidazolium) cations [C₈H₁₂(CH₂)_nN₄Br₂] (<i>n</i> = 1–6, <b>a</b>–<b>f</b>). In this series of ion-pair compounds <b>1a</b>–<b>1f</b>, a common [Cu­(mnt)₂]^2– complex anion is associated with alkyl imidazolium cations of varied alkyl chain lengths. We have described a systematic study of deviation from square planar geometries (in terms of distortion) around the metal ion in customary square planar metal-dithiolene complexes. The distortion in the geometry around the metal ion can be explained on the basis of center of symmetry along C–H···Cu supramolecular interaction and unbalanced supramolecular interactions, such as S···H, N···H, and M···S type weak contacts. Dianionic copper­(II) complexes <b>1a</b>–<b>1f</b> show an electronic absorption in the near-infrared (NIR) region, which has been attributed to the charge transfer transition from the highest occupied molecular orbital level of copper dithiolate anion [Cu­(mnt)₂]^2– to the lowest unoccupied molecular orbital level of alkyl imidazolium cation [C₈H₁₂(CH₂)_<i>n</i>N₄]²⁺. All these compounds are unambiguously characterized by single crystal X-ray crystallography and further characterized by IR, ¹H NMR, electron spin resonance, LC/MS spectroscopic techniques, and electrochemical studies

Acid-base behavior of a simple metal bis(dithiolate) system: synthesis, crystal structure and spectroscopy of [Bu<SUB>4</SUB>N]<SUB>2</SUB>[M<SUP>II</SUP>(ppdt)<SUB>2</SUB>] (M = Ni, Pt; ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate)

The syntheses, crystal structures and properties of compounds [Bu4N]2[Ni(ppdt)2] (1) and [Bu4N]2[Pt(ppdt)2] (2) (ppdt = pyrido[2,3-b]pyrazine-2,3-dithiolate) have been described. Compound 1 crystallizes in P21/c space group (monoclinic system), whereas compound 2 crystallizes in C2/c space group (monoclinic system). The crystal structures of both compounds 1 and 2 have been characterized by C-HS and C-HN hydrogen bonding interactions between cation and anions resulting in three-dimensional supramolecular networks in the crystals of 1 and 2, respectively. The acid-base behavior of the ground states of both [Bu4N]2[Ni(ppdt)2] (1) and [Bu4N]2[Pt(ppdt)2] (2) and also the excited state of compound [Bu4N]2[Pt(ppdt)2] (2) in solutions has been studied. The pH dependent changes in the charge transfer absorption and emission spectra are attributed to the protonation on an imine nitrogen of the ppdt ligand. The ground-state basicity constants of the two complexes 1 and 2 have been determined from spectrophotometric analysis by titrating with an weak acid, yielding pKb1 = 8.0 for complex [Bu4N]2[Ni(ppdt)2] (1) and pKb1 = 7.8 for complex [Bu4N]2[Pt(ppdt)2] (2). The excited-state basicity constant pKb1 for complex [Bu4N]2[Pt(ppdt)2] (2) has been determined by a thermodynamic equation using a Forster analysis yielding the value of 1.8. The complex 2 is electrochemically irreversible with an oxidation potential of E1/2 = +0.41 V versus Ag/AgCl in methanol

Understanding the formation of metal-oxide based inorganic solids: assessing the influence of tetrazole molecule

The hydrothermal reaction of Cu(II) salt, ammonium heptamolybdate and 4-ptz (5-(4-pyridyl) tetrazole) at different synthetic conditions yields two compounds [Cu(4-Hptz)(Mo<SUB>2</SUB>O<SUB>7</SUB>)] (1) and [Cu(4-Hptz)<SUB>2</SUB>(H<SUB>2</SUB>O)<SUB>3</SUB>]2[Mo<SUB>8</SUB>O<SUB>26</SUB>] (2). Both the compounds 1 and 2 are characterized by routine elemental analyses, IR-, thermogravimetric studies and unambiguously characterized by single crystal X-ray crystallography. Compound 1 exhibits a 3D bimetallic oxide framework, constructed from the tetrazoles and {CuMo<SUB>2</SUB>O<SUB>7</SUB>} oxide phase. The coordination ability of nitrogen atoms in the tetrazole ring makes the ring acting as a template in the formation of {Cu<SUB>4</SUB>Mo<SUB>6</SUB>O<SUB>10</SUB>} rings, made up of [Mo<SUB>2</SUB>O<SUB>7</SUB>]<SUP>2-</SUP> anions and Cu(II) octahedra; the stacking of these {Cu<SUB>4</SUB>Mo<SUB>6</SUB>O<SUB>10</SUB>} rings along crystallographic c axis results in the formation of 3D bimetallic oxide framework. Compound 2 consists of infinite octamolybdate chains and Cu-tetrazolate complex cation. The formation of oxide phase under hydrothermal conditions is discussed, giving importance of the role of geometry of the tetrazole ring

Ion-pair charge transfer complex with near-IR absorption: Synthesis, crystal structure and properties of [Hb]<SUB>2</SUB>[Cu(mnt)<SUB>2</SUB>] (Hb = 1-(4-((1H-imidazol-1-yl)methyl)benzyl)-1H-imidazol-3-ium)

The compound [Hb]2[Cu(mnt)2] (1) [Hb = 1-(4-((1H-imidazol-1-yl)methyl)benzyl)-1H-imidazol-3-ium] has been synthesized, starting from 1,4-bis((1H-imidazol-1-yl)methyl)benzene, cupric chloride, and Na2mnt in methanol. Compound 1 crystallizes in monoclinic system with C2/c space group. In the crystal structure, the interactions between cations and anions via bifurcated C—H···(NC-mnt)2 hydrogen bonds give rise to a two dimensional supramolecular network. It has also been observed that two cation moieties (Hb) are attached together by a very short C—H···N hydrogen bonding interaction with H...N distance of 1.74 Å, ∠ CHN bond angle of 174.9°. Compound 1 is additionally characterized by cyclic voltammetry, UV-Vis, IR, 1H NMR and EPR spectroscopy. The ion-pair compound 1 shows an intense absorption in the near-IR region at ~1214 nm which has been described as a charge transfer band from HOMO of the copper dithiolate anion [Cu(mnt)2]2-, to LUMO of the [Hb]+ cation. The title compound exhibits an oxidative response at +0.46 V vs. Ag/AgCl and a reductive event at -0.67 V vs. Ag/AgCl

Significant Role of Supramolecular Interactions on Conformational Modulation of Flexible Organic Cation Receptors in a Metal-Bis(dithiolate) Coordination Complex Matrix

A series of new ion-pair complexes [Bz,R-BzBimy]₂[M­(mnt)₂] {[Bz,R-BzBimy]⁺ = 1-benzyl-3-(4-R-benzyl)­benzimidazolium; M = Cu, R = H (<b>1a</b>), NO₂ (<b>1b</b>) and Br (<b>1c</b>); M = Ni, R = H (<b>2a</b>), NO₂ (<b>2b</b>) and Br (<b>2c</b>) and mnt^2– = maleonitriledithiolate} have been prepared and characterized by routine spectral analyses including single crystal X-ray crystallography. Due to the flexible nature of aryl groups (−CH₂–Ar) in benzimidazolium cations, [Bz,H-BzBimy]¹⁺ and [Bz,NO₂-BzBimy]¹⁺ of compounds [Bz,H-BzBimy]­BF₄ (<b>a</b>) and [Bz,NO₂-BzBimy]­BF₄ (<b>b</b>), respectively, the conformational change of the aryl groups have been observed in their respective metal-dithiolate compounds <b>1a</b>, <b>1b</b>, <b>2a</b>, and <b>2b</b>. However, no change in orientation of the associated phenyl groups is observed between the cationic organic receptor [Bz,Br-BzBimy]¹⁺ of compound [Bz,Br-BzBimy]₂BF₄ (<b>c</b>) and that in resulting ion pair compounds <b>1c</b> and <b>2c</b>. Fluxional behavior of the aryl groups in the cationic organic receptor (benzimidazolium moiety, [Bz,R-BzBimy]⁺), when it is ion-paired with different counteranions, e.g., tetrafluoroborate (BF₄^–) and [M­(mnt)₂]^2–, is mainly dependent on the supramolecular interactions (for example, S···H, N···H, O···H, Br···Br, etc., weak contacts) between the relevant cation and anion. The <i>p</i>-substituents (H, NO₂, and Br) of one of the phenyl rings in benzimidazolium moiety (cationic part) are found to be responsible for the structural diversities, observed in the crystal structures of metal-dithiolate ion pair compounds <b>1a</b>, <b>1b</b>, <b>1c</b>, <b>2a</b>, <b>2b</b>, and <b>2c</b>. In this context, it is worth mentioning that the nickel containing ion pair compounds <b>2a</b>, <b>2b</b>, and <b>2c</b> are isomorphous with corresponding copper analogues <b>1a</b>, <b>1b</b>, and <b>1c</b>. The near-IR absorbance bands at around 1210 nm, observed for the copper compounds (<b>1a</b>–<b>1c</b>), have been attributed to the charge transfer from the copper dithiolate anion [Cu­(mnt)₂]^2– to the benzimidazolium cation [Bz,R-BzBimy]⁺. The absorption bands, observed at around 862 nm for nickel compounds (<b>2a</b>–<b>2c</b>), can be assigned to combined transitions consisting of d–d, MLCT, π → π* electronic transitions. DFT calculations have been carried out to determine stability of bare organic molecules, used in this study, in the perspective of their apparent stability (energy consideration) in the matrix of metal dithiolate coordination complex. Hirshfeld surface analyses have been performed to assess additional supramolecular perceptions into crystal structure features. The relevant fingerprint plot areas portray the percentages of different intermolecular interactions in the crystal structures. Copper compounds <b>1a</b>–<b>1c</b> are additionally characterized by electron spin resonance (ESR) studies

An Organic Receptor Isolated in an Unusual Intermediate Conformation: Computation, Crystallography, and Hirshfeld Surface Analysis

1,1″-1,4-Phenylene-bis­(methylene)­bis-4,4′-bipyridinium cation [C₂₈H₂₄N₄]²⁺ (<b>c</b>), an organic receptor that generally crystallizes in its anti conformation, has recently been shown to be isolated in its syn conformation in an ion-paired compound [C₂₈H₂₄N₄]­[Zn­(dmit)₂]·2DMF (dmit^2– = 1,3-dithiole-2-thione-4,5-dithiolate; DMF = dimethylformamide). In this article, we demonstrated that the same receptor [C₂₈H₂₄N₄]²⁺ (<b>c</b>) can also be stabilized in an unusual intermediate conformation (neither syn nor anti) with PF₆^– anion in compound [C₂₈H₂₄N₄]­(PF₆)₂·(1,4-dioxane) (<b>1</b>·(1,4-dioxane)). The energetically favored anti conformation has been described in its nitrate salt [C₂₈H₂₄N₄]­(NO₃)₂·2H₂O (<b>2</b>·2H₂O). Compounds <b>1</b>·(1,4-dioxane) and <b>2</b>·2H₂O, crystallizing in triclinic and monoclinic systems with space groups <i>P</i>1̅ and <i>P</i>2₁/<i>n</i>, respectively, were additionally characterized by Hirshfeld surface analysis. The density functional theory calculations are performed to understand the internal mechanism of the stability of various conformers of cationic receptor <b>c</b>, compound <b>1</b>, and compound <b>2</b>. In conjunction with the electronic stability of the conformers, the natural bond orbital analysis and conformational equilibrium constants at different temperatures are also calculated to find out the sources of the different stability of the various conformers of experimentally synthesized compounds