Cationic Units Research Articles

Hydrothermal Syntheses, Crystal Structures, and Fluorescent Properties of Zn(II) Coordination Complexes With 4-Amino-3,5-Bis(2-Pyridyl)-1,2,4-Triazole and Different Aromatic Dicarboxylic Acids

Three new Zn(II) supramolecular complexes {[Zn(2-bpt)(tp)(H2O)](H2O)}∞ (1), [Zn(2-bpt)2(Hpa)2] (2), and [Zn(2-bpt)2(H2O)2](Hip-NO2)2 (3) have been synthesized under hydrothermal conditions by using 4-amino-3,5-bis(2-pyridyl)- 1,2,4-triazole (2-bpt) and Zn(OAc)2 with the presence of different aromatic dicarboxylic acids (H2tp = terephthalic acid, H2pa = phthalic acid, and H2ip–NO2 = 5-nitroisophthalic acid). Complex 1 shows a one-dimensional zigzag chain array, 2 represents a neutral mononuclear molecule, and 3 consists of the cationic mononuclear coordination unit and Hip-NO2 anion. Notably, in complex 3, the H2ip–NO2 ligand is partly deprotonated to balance the charge and uncoordinated to the metal center. In all three structures, the low-dimensional coordination motifs are further extended to distinct two-dimensional or three-dimensional supramolecular networks via H-bonding and/or π···π stacking interactions. Fluorescent properties for 1–3 have also been studied in solid state at room temperature.

Water clusters in mixed ionic complexes with metal dipicolinate anions

Formations of three different types of hydrogen-bonded water clusters in the interstices of mixed ionic complexes with metal dipicolinate anions are reported. In the complex [Co(phen)2(H2O)2][Zn(dpa)2]⋅7H2O (1) (where phen=1,10-phenanthroline, dpa=dipicolinate), both the cation and anion is hydrophilic in nature, exhibits an unusual 2D infinite cyclic water decamers (H2O)10 stabilized by four identical zinc dipicolinato complex anions. Modulating the cationic unit to a hydrophobic environment by replacing the aqua ligand with 2,2′-bipyridine ligand the water cluster can be modified. The complex [Ni(phen)2⋅bpy][Co(dpa)2]⋅8H2O (2) (where bpy=2,2′-bipyridine) has unprecedented discrete hydrogen bonded hexadecameric (H2O)16 water clusters encapsulated between eight anionic units. A rare wavelike infinite water chain (H2O)n is observed in complex [Co(phen)3][Mn(dpa)2]⋅12H2O (3), in this case the water chain fills the interstitial space created by packing of large hydrophilic anionic units and hydrophobic cationic units. The reported clusters are indefinitely stable in their respective complex at ambient temperature, but the water loss is irreversible when thermally decomposed.

(Dimethylphosphoryl)methanaminium chloride

The crystal structure of the title salt, C3H11NOP+·Cl−, is primarily built from centrosymmetric dimers of two cations, connected head-to-tail by two charge-supported strong N—H⋯O hydrogen bonds, with a graph-set descriptor R 2 2(10). The chloride counter-anions connect these dimeric cationic units into chains along the a-axis direction.

μ-4,4′-Bipyridine-κ2N:N′-bis[tetraaqua(4,4′-bipyridine-κN)dimanganese(II)] bis(4-aminobenzoate) bis(perchlorate)–4,4′-bipyridine–water (1/2/4): a supramolecular system constructed by π–π and hydrogen-bond interactions

The title dinuclear manganese compound, [Mn(2)(C(10)H(8)N(2))(3)(H(2)O)(8)](C(7)H(6)NO(2))(2)(ClO(4))(2)·2C(10)H(8)N(2)·4H(2)O, (I), has an inversion center located midway between the Mn(II) ions. Each Mn(II) ion has a distorted octahedral coordination environment, defined by two mutually cis N atoms from two different 4,4'-bipyridine (4,4'-bipy) ligands and four O atoms from four water molecules. The asymmetric unit contains cationic [Mn(4,4'-bipy)(1.5)(H(2)O)(4)](2+), one isolated 4,4'-bipy molecule, one 4-aminobenzoate ion, one disordered perchlorate ion and two uncoordinated water molecules. In the dinuclear manganese cationic unit, one 4,4'-bipy acts as a bidentate bridging ligand between two Mn(II) ions, while the other two act only as monodentate terminal ligands, giving rise to a 'Z-type' [Mn(2)(4,4'-bipy)(3)(H(2)O)(8)] host unit. These host units are linked to each other via face-to-face π-π stacking interactions between monodentate terminal 4,4'-bipy ligands, generating a zigzag chain. The corners of these chains, defined by Mn(OH)(4) units, are surrounded by the solvent water molecules and the carboxylate O atoms of the 4-aminobenzoate ions, and all of these are connected to each other via strong O-H···O hydrogen-bond interactions, leading to a three-dimensional grid network with a large cavity running along the b axis of the unit cell. The isolated 4,4'-bipy molecules, the 4-aminobenzoate and perchlorate anions and the water molecules are encapsulated in the cavities by numerous hydrogen-bond interactions.

Unusual Very Strong O–H···O Hydrogen Bonding in Zinc Complex: Crystal Structure and Photoluminescence of [Zn(HL)(bpy)2(H2O)]2(L) (L = O2C(CF2)6CO2, bpy = 2,2′bipyridine)

The centrosymmetric dimer zinc compound, [Zn(HL)(bpy)2(H2O)]2(L), (L = O2C(CF2)6CO2, bpy = 2,2′-bipyridine), was obtained through the reaction of Zn(ClO4)2·6H2O, bpy and perfluorosuberic acid. Zn(II) centre is coordinated by four N atoms from two bpy ligands and two O atoms from a water molecule and monoanionic suberate ligand in a distorted octahedral coordination environment. The unit structure contains crystallographically centrosymmetric suberate anion which acts as a bidentate bridging ligand between each cationic monomer complex unit via hydrogen bonding. The very strong interaction of hydrogen bonding of hydoxycarbonyl–carboxylate system in solid state has O–H···O 2.436(3) A (O···H = 1.25(6) A and H···O = 1.19(6) A). These units are also connected to each other via π···π, C–H···π, C–F···π and F···F stacking interactions, C–H···O, O–H···O and C–H···F hydrogen bonds giving rise to a multi-dimensional network. The complex is the first reported example of a coordination compound based on both bpy ligands together with perfluorosuberic acid. Moreover, compound exhibit intense solid state fluorescent emissions at room temperature. The synthesis and X-ray characterization of unusual centrosymmetric dimer zinc compound, [Zn(HL)(bpy)2(H2O)]2(L) (L = O2C(CF2)6CO2, bpy = 2,2′bipyridine), and its photoluminescence property have been reported. The very strong interaction of hydrogen bonding of hydroxycarbonyl-carboxylate system in solid state has O–H···O 2.436(4) A (O···H = 1.25 (7) A, H···O = 1.20(7) A and OHO = 168.4°).

Tetranuclear Zn(II) complexes with compartmental and dicyanamido ligands: synthesis, structure, and luminescent properties

New tetranuclear compounds have been obtained by reacting binuclear complexes, [Zn2L n (μ-OH)(H2O)2](ClO4)2, with sodium dicyanamide (HL n are end-off bicompartmental ligands resulting from condensation between 2,6-diformyl-p-cresol with N,N-dimethyl-ethylenediamine or 2-aminomethyl-pyridine). The complexes, [{L1(μ-OH)Zn2}(μ 1,5-dca)2{Zn2(μ-OH)L1}](ClO4)2 (1) and [{Zn2L2(μ 3-OH)(dca)}2](ClO4)2 · 2H2O (2), have been characterized by single-crystal X-ray diffraction. The angular nature of the bridging dicyanamido induces the “M” shape of the tetranuclear cationic unit in 1. The tetranuclear cation, because of its particular shape, acts as a receptor toward one perchlorate ion, which is hydrogen bonded to the hydroxo groups. This tetranuclear unit in 2 has a defective heterocubane structure. The luminescence properties of the new tetranuclear complexes have been investigated.

Diaquabis(pyrazine-2-carboxamide-κ2N1,O)cobalt(II) dinitrate

The asymmetric unit of the title complex, [Co(C5H5N3O)2(H2O)2](NO3)2, contains one half of a CoII cationic unit and a nitrate anion. The entire [Co(C5H5N3O)2(H2O)2]2+ cationic unit is completed by the application of inversion symmetry at the CoII site, generating a six-coordinate distorted octa­hedral environment for the metal ion. The chelating pyrazine-2-carboxamide mol­ecules are bound to cobalt via N and O atoms, forming a square plane, while the remaining two trans positions in the octa­hedron are occupied by two coordinated water mol­ecules.

A dinuclear manganese(III) and a rare pentanuclear manganese(III) compound with a phenol–pyrazole ligand

Reacting Mn(ClO4)2·6H2O and H2phpzEt (H2phpzEt=5(3)-(2-hydroxyphenyl)-3(5)-ethylpyrazole) in methanol in the presence of sodium hydroxide yields the compound [Mn2(HphpzEt)4(H2O)2](ClO4)2 (1). The pentanuclear [Mn5(μ3-O)2(HphpzEt)3(phpzEt)3(OCH3)(HOCH3)2(O2CPh)] (2) is obtained when performing a similar reaction with Mn(O2CPh)2·2H2O. Compound 1 consists of a symmetric dinuclear manganese(III) cationic unit, [Mn2(HphpzEt)4(H2O)2]2+ with two non-coordinated perchlorate anions. Compound 2 is a rare pentanuclear complex containing all the manganese ions in the oxidation state III and it also has μ3-oxido ligands. Temperature- and field-dependent magnetization studies indicate dominant antiferromagnetic interactions between the manganese(III) ions in both compounds.

Adsorption of cationic polymers on the surfaces of anionic glass microspheres

The adsorption of cationic copolymers prepared by the quaternization of poly(4-vinylpyridine) with bromoacetic acid and/or ethyl bromide on the surface of anionic glass microspheres and the stability of the as-prepared complexes against dissociation in water-salt solutions are studied. Experiments are performed with the use of two types of copolymers: copolymers carrying cationic and hydrophobic units and copolymers carrying cationic and zwitterionic (electroneutral) units in main chains. For hydrophobic copolymers, the limiting adsorption decreases as the molar fraction of cationic groups in the copolymer, α, increases. In the case of hydrophilic copolymers, the dependence of limiting adsorption on α has a bellshaped pattern with a maximum at α = 0.15 and a horizontal segment at α > 0.4. Hydrophobic copolymers feature irreversible binding with microspheres at α > 0.24; hydrophilic copolymers, at α ≥ 0.15. The obtained data may be used for creation of biocidal polymer coatings and sorption layers that reversibly desorb from the surface with a change in the salt concentration in the surrounding aqueous solution.

Characterization and optimization of an online system for the simultaneous measurement of atmospheric water-soluble constituents in the gas and particle phases

In this work we present the results of extensive characterization and optimization of the Ambient Ion Monitor-Ion Chromatograph (AIM-IC) system, an instrument developed by URG Corp. and Dionex Inc. for simultaneous hourly measurements of the water-soluble chemical composition of atmospheric fine particulate matter (PM(2.5)) and associated precursor gases. The sampling assembly of the AIM-IC consists of an inertial particle size-selection assembly, a parallel-plate wet denuder (PPWD) for the collection of soluble gases, and a particle supersaturation chamber (PSSC) for collection of particles, in series. The analytical assembly of the AIM-IC consists of anion and cation IC units. The system detection limits were determined to be 41 ppt, 5 ppt, and 65 ppt for gas phase NH(3(g)), SO(2(g)), and HNO(3(g)) and 29 ng m(-3), 3 ng m(-3), and 45 ng m(-3) for particle phase NH(4)(+), SO(4)(2-), and NO(3)(-) respectively. From external trace gas calibrations with permeation sources, we determined that the AIM-IC is biased low for NH(3(g)) (11%), SO(2(g)) (19%), and HNO(3(g)) (12%). The collection efficiency of SO(2(g)) was found to strongly depend on the composition of the denuder solution and was found to be the most quantitative with 5 mM H(2)O(2) solution for mixing ratios as high as 107 ppb. Using a cellulose membrane in the PPWD, the system responded to changes in SO(2(g)) and HNO(3(g)) within an hour, however for NH(3(g)), the timescale can be closer to 20 h. With a nylon membrane, the instrument response time for NH(3(g)) was significantly improved, becoming comparable to the responses for SO(2(g)) and HNO(3(g)). Performance of the AIM-IC for collection and analysis of PM(2.5) was evaluated by generating known number concentrations of ammonium sulfate and ammonium nitrate particles (with an aerodynamic diameter of 300 nm) under laboratory conditions and by comparing AIM-IC measurements to measurements from a collocated Aerosol Mass Spectrometer (AMS) during a field-sampling campaign. On average, the AIM-IC and AMS measurements agreed well and captured rapid ambient concentration changes at the same time. In this work we also present a novel inlet configuration and plumbing for the AIM-IC which minimizes sampling inlet losses, reduces peak smearing due to sample carryover, and allows for tower-height sampling from the base of a research tower.

Nitron: a stable N-heterocyclic carbene that has been commercially available for more than a century

The analytical reagent Nitron is a mesoionic compound whose structure consists of a cationic triazolium unit with an anionic PhN substituent. We provide clear evidence for the existence of a singlet diaminocarbene tautomer whose structure is composed of a 1,2,4-triazol-5-ylidene unit bearing an NHPh substituent.

Synthesis, crystal structure and magnetism of new salicylamidoxime-based hexanuclear manganese(iii) single-molecule magnets

Salicylamidoxime was used to synthesize 13 new polynuclear Mn(III) complexes. We present the crystallographic structures, the magnetic susceptibility and the magnetization measurements of eight of them (1-8) with the general formula [Mn(6)O(2)(H(2)N-sao)(6)(L)(2)(solvent)(4-6)] (L = carboxylate, chloride, 2-cyanophenolate; solvent = H(2)O, MeOH, EtOH, py). These complexes consist of two trinuclear {Mn(III)(3)(μ(3)-O)(H(2)N-sao)(3)}(+) cationic units linked together via two oximate and two phenolate oxygen atoms. All behave as single-molecule magnets, with the spin ground state varying from 4 to 12 and anisotropy energy barriers from 24 to 86 K, the latter being as high as the present record barrier in the Mn(6) complexes. DFT calculations were performed to compute the exchange magnetic coupling constants J between the metallic ions and to provide an orbital interpretation of exchange. Our results are in line with previously reported results with the parent salicylaldoxime derivatives. The Mn-N-O-Mn torsion angle appears as the main parameter controlling the J values. The critical angle where the exchange coupling between two Mn(III) switches from antiferromagnetic to ferromagnetic is 27°, less than the one found in related complexes with salicylaldoxime (30°). We propose a structural classification of the {Mn(6)} complexes in four classes depending on the coordination of the axial carboxylate. The work points out the structural flexibility of such systems, their sensitivity to solvent effects and their ability to achieve high anisotropy energy barriers by simple desolvation.

A Further Extension of Pnictide Oxide Chemistry – Synthesis and Structure of La2AuP2O

AbstractThe phosphide oxide La2AuP2O was synthesized from lanthanum filings, dried La2O3, gold pieces, and ground red phosphorus in the ideal 1.33:0.33:1:2 ratio in an evacuated silica tube at 1473 K. Small single crystals were obtained by recrystallization in a NaCl/KCl flux. The structure was determined on the basis of single‐crystal X‐ray diffractometer data: new type, C2/m, a = 1537.3(3), b = 427.39(8), c = 1009.2(2) pm, β = 131.02(1) °, wR2 = 0.046, 1102 F2 values, 38 variables. La2AuP2O contains two striking structural motifs: The oxygen atoms are located in La4 tetrahedra. The latter are cis‐edge‐shared forming polymeric cationic [La2O]4+ chains. These cationic units are separated and charge‐balanced by [AuP2]4– polyanions which have monovalent gold in distorted trigonal planar phosphorus coordination. Two crystallographically independent phosphorus sites occur in the polyanion, i.e. isolated P3– besides dumb‐bells P24– (P2–P2 223 pm). La2AuP2O, which crystallizes in the form of ruby red transparent crystals, is an electron precise phosphide oxide (4La3+)(2Au+)(2P3–)(P24–)(2O2–).

Supramolecular Assemblies of Histidinylated α-Cyclodextrin in the Presence of DNA Scaffold during CDplexes Formation

α-Cyclodextrin was transformed in a cationic unit after per substitution with histidine (His-α-CD) and lysine (Lys-α-CD) molecules on the primary face. His-α-CD and Lys-α-CD were used to form electrostatic complexes (CDplexes) with a plasmid DNA encoding luciferase gene, and the ability of CDplexes to transfect mammalian cells was examined using HEK293-T7 cells. The luciferase activity in cells transfected with His-α-CDplexes was 8-fold higher than that obtained Lys-α-CDplexes. When the transfection was carried out in the presence of chloroquine, the luciferase activity with His-α-CDplexes and Lys-α-CDplexes increased 6 and 25 times, respectively. The lower enhancement with His-α-CDplexes confirmed that histidine induced a proton sponge effect inside endosomes upon imidazole protonation, favoring DNA delivery in the cytosol. At the same time, we found that the condensation of DNA with His-α-CD was unexpectedly stronger than that obtained with the lysyl-α-CD counterpart. Moreover, it was as strong as that observed with high molecular weight polylysine. NMR (ROESY and DOSY) investigations in the absence of DNA showed that an inclusion complex is formed between the imidazole ring of histidine and the hydrophobic cavity of CD but no His-α-CD polymers can be formed by intermolecular interactions. These results suggest that intermolecular interactions between imidazole and His-α-CD cavity could be involved to form supramolecular assemblies in the presence of a DNA scaffold leading to DNA condensation into low diameter particles.

The “Missing Link”: The Gas-Phase Generation of Platinum-Methylidyne Clusters PtnCH+ (n=1, 2) and Their Reactions with Hydrocarbons and Ammonia

Electrospray ionization (ESI) of tetrameric platinum(II) acetate, [Pt(4)(CH(3)COO)(8)], in methanol generates the formal platinum(III) dimeric cation [Pt(2)(CH(3)COO)(3)(CH(2)COO)(MeOH)(2)](+), which, upon harsher ionization conditions, sequentially loses the two methanol ligands, CO(2), and CH(2)COO to form the platinum(II) dimer [Pt(2)(CH(3)COO)(2)(CH(3))](+). Next, intramolecular sequential double hydrogen-atom transfer from the methyl group concomitant with the elimination of two acetic acid molecules produces Pt(2)CH(+) from which, upon even harsher conditions, PtCH(+) is eventually generated. This degradation sequence is supported by collision-induced dissociation (CID) experiments, extensive isotope-labeling studies, and DFT calculations. Both PtCH(+) and Pt(2)CH(+) react under thermal conditions with the hydrocarbons C(2)H(n) (n=2, 4, 6) and C(3)H(n) (n=6, 8). While, in ion-molecule reactions of PtCH(+) with C(2) hydrocarbons, the relative rates decrease with increasing n, the opposite trend holds true for Pt(2)CH(+). The Pt(2)CH(+) cluster only sluggishly reacts with C(2)H(2), but with C(2)H(4) and C(2)H(6) dihydrogen loss dominates. The reactions with the latter two substrates were preceded by a complete exchange of all of the hydrogen atoms present in the adduct complex. The PtCH(+) ion is much less selective. In the reactions with C(2)H(2) and C(2)H(4), elimination of H(2) occurs; however, CH(4) formation prevails in the decomposition of the adduct complex that is formed with C(2)H(6). In the reaction with C(2)H(2), in addition to H(2) loss, C(3)H(3)(+) is produced, and this process formally corresponds to the transfer of the cationic methylidyne unit CH(+) to C(2)H(2), accompanied by the release of neutral Pt. In the ion-molecule reactions with the C(3) hydrocarbons C(3)H(6) and C(3)H(8), dihydrogen loss occurs with high selectivity for Pt(2)CH(+), but in the reactions of these substrates with PtCH(+) several reaction routes compete. Finally, in the ion-molecule reactions with ammonia, both platinum complexes give rise to proton transfer to produce NH(4)(+); however, only the encounter complex generated with PtCH(+) undergoes efficient dehydrogenation of the substrate, and the rather minor formation of CNH(4)(+) indicates that C-N bond coupling is inefficient.

Synthesis, binding and cellular uptake properties of oligodeoxynucleotides containing cationic bicyclo-thymidine residues

The synthesis and incorporation into oligodeoxynucleotides of two novel derivatives of bicyclothymidine carrying a cationic diaminopropyl or lysine unit in the C(6′)-β position is described. Compared to unmodified DNA these oligonucleotides show T m-neutral behavior when paired against complementary DNA and are destabilizing when paired against RNA. Unaided uptake experiments of a decamer containing five lys-bcT units into HeLa and HEK293T cells showed substantial internalization with mostly cytosolic distribution which was not observed in the case of an unmodified control oligonucleotide.

Two transition metal coordination polymers constructed from 3-aminobenzoate and 4,4′-bipyridine

Two new transition metal coordination polymers, [Zn(abz)(bipy)](ClO4) (1) and [Mn(bipy)5(H2O)6](ClO4)2 · 2(abz) · 2(H2O) (2) (bipy = 4,4′-bipyridine, abz = 3-aminobenzoate), were prepared and characterized by elemental analysis, FTIR spectroscopy, and single-crystal X-ray diffraction. Complex 1 is a 2-D-layered network with a (4,4) net built up by bipy and 3-aminobenzoate ligands connecting two zinc nodes. Complex 2 is a 3-D supramolecular grid network constructed from close stacking bipy ligands of H-type cation units with large cavities hosting 3-aminobenzoate, perchlorate ions, and water. Solid state photoluminescence for 1 was also investigated.

Cationic Mn4 Single-Molecule Magnet with a Sterically Isolated Core

The synthesis, structure, and magnetic properties of a ligand-modified Mn(4) dicubane single-molecule magnet (SMM), [Mn(4)(Bet)(4)(mdea)(2)(mdeaH)(2)](BPh(4))(4), are presented, where the cationic SMM units are significantly separated from neighboring molecules in the crystal lattice. There are no cocrystallized solvate molecules, making it an ideal candidate for single-crystal magnetization hysteresis and high-frequency electron paramagnetic resonance studies. Increased control over intermolecular interactions in such materials is a crucial factor in the future application of SMMs.

Bis(1-methylpiperazine-1,4-diium) tetrachloridocuprate(II)

The title compound, (C5H14N2)[CuCl4], was synthesized by hydro­thermal reaction of CuCl2 with 1-methyl­piperazine in an HCl/water solution. Both amine N atoms are protonated. The piperazine ring adopts a chair conformation. The Cu—Cl distances in the tetrahedral anion are in the range 2.2360 (7)–2.2732 (7) Å. In the crystal, moderately strong and weak inter­molecular N—H⋯Cl hydrogen bonds link the anion and cation units into an infinite two-dimensional network parallel to the ab plane.

Bis(1-methylpiperazine-1,4-diium) tetrabromidocuprate(II)

The title compound, (C5H14N2)[CuBr4], was synthesized by hydro­thermal reaction of CuBr2 with 1-methyl­piperazine in an HBr/water solution. Both amine N atoms are protonated. The Cu—Br distances in the tetrahedral anion are in the range 2.3809 (11)–2.4131 (11) Å. In the crystal, moderately strong and weak inter­molecular N—H⋯Br hydrogen bonds link the anion and cation units into an infinite two-dimensional network parallel to the ab plane.