Unusual one-dimensional branched-chain structures assembled by a novel imidazole-containing tripodal ligand with cadmium(II) salts and their fluorescent property

Three novel coordination polymers [Cd₃(L)₂(μ-Br)(μ-Cl)Br₃Cl] (1), [Cd₃(L)₂(μ-Cl)₂Cl₄] (2) and [Cd(L)Cl]₂[CdCl₄]·H₂O (3) were obtained by reactions of an imidazole-containing tripodal ligand N¹-(2-aminoethyl)-N¹-(2-imidazolethyl)-ethane-1,2-diamine (L) with Cd(II) salts. Their structures were determined by X-ray crystallography. Crystal data for 1, monoclinic system, P2₁/c, a=7.752(4) Å, b=31.70(2) Å, c=14.012(7) Å, β=109.439(7)°, V=3247(3) Å³, Z=4. 2, monoclinic system, P2₁/c, a=7.6564(15) Å, b=31.433(6) Å, c=13.925(3) Å, β=109.89(3)°, V=3151.1(11) Å³, Z=4. 3, orthorhombic system, Pbcn, a=22.950(2) Å, b=8.435(7) Å, c=17.360(2) Å, V=3360.3(51) Å³, Z=4. Complexes 1 and 2 have similar one-dimensional (1D) branched-chain structure while complex 3 features a 1D zigzag cationic chain with [CdCl₄]²⁻ serving as counter anion. The photoluminescent measurements reveal that all the complexes exhibit blue fluorescence at room temperature in the solid state.     

Structural characterization of [Fe(NO)(mnt)2] salts

The iron dithiolene compounds [Fe₂(mnt)₄]²⁻ [1]²⁻ and [Fe(NO)(mnt)₂]ⁿ (n = 1−, [2]¹⁻; n = 2−, [2]²⁻) ([mnt]²⁻ = maleonitriledithiolate = [(NC)₂C₂S₂]²⁻) have been characterized structurally by X-ray diffraction as their [Et₄N]⁺ salts at 100 K. Dianion [2]²⁻ is prepared from [2]¹⁻ by reduction with Na[Et₃BH] and is observed to have a bent Fe-NO angle at 149.9(5)° in contrast to the linear configuration of Fe-NO in [2]¹⁻ (180.0°). The change from linear to bent binding mode for NO, an increase of more than 0.1 Å in the Fe-N bond length, and the relative invariance of the Fe-S distances for [2]²⁻ versus [2]¹⁻ indicate that the NO ligand is the site of reduction. The [Et₃NH]⁺ complex of [2]¹⁻ was also identified by crystallography and found to have hydrogen bonding contacts between [Et₃NH]⁺ and the cyano nitrogen atom of an [mnt]²⁻ ligand. Furthermore, relatively close S?S contacts (3.602-3.615 Å) occur between [2]¹⁻ anions, which pack together in an offset, head-to-head fashion. These S?S contacts are absent in the structure of [Et₄N][2]. Infrared spectra show an energy decrease for, and a significant broadening of, the NO bond stretching absorption peak in [2]²⁻, which is consistent with a bent NO ligand sampling a range of conformations both by facile pivoting about the Fe-N axis and by a breathing of the Fe-NO angle.     

Cation-controled formation of N,N′-dialkylimidazolium cadmium-thiocyanate complexes: synthesis and structural characterization

Three new N,N′-dialkylimidazolium salts of cadmium-thiocyanate, [EtMeIm]₂[Cd₂(SCN)₆] (2), [C₆H₄(CH₂ImMe)₂][Cd(SCN)₄] (3), [C₆Me₃(CH₂ImMe)₃][CdBr₃(SCN)](NO₃) (4) have been prepared, and their crystal structures have been determined by X-ray diffraction. Crystal data: 2, monoclinic, C2/c, a=18.349(4) Å, b=7.8667(18) Å, c=21.399(5) Å, β=110.346(4)°, V=2896.1(11) Å³, Z=4, and R1=0.0561; 3, monoclinic, C2/c, a=20.347(7) Å, b=14.029(5) Å, c=9.380(3) Å, β=112.034(6)°, V=2482.1(15) Å³, Z=4, and R1=0.0397; 4, hexagonal, P6₃, a=b=10.7634(8) Å, c=16.0315(17) Å, V=1608.4(2) Å³, Z=2, and R1=0.0569. Compound 2 consists of triply bridged infinite one-dimensional cadmium-thiocyanate chains, and two independent cadmium atoms are octahedrally coordinated in 2N4S and 4N2S geometry, respectively. In 3, the cadmium atom is octahedrally coordinated with two cis N-bonded monodentate NCS⁻ ligands and four bridging SCN⁻ in a S trans to S, and N trans to N coordination fashion, and thus form doubly bridged infinite one-dimensional chains. Whereas 4 is mononuclear, consisting of a discrete [C₆Me₃(CH₂ImMe)₃]³⁺ cation, a nitrate, and [CdBr₃(SCN)]⁻ ion, and each cadmium(II) ion is coordinated to three bromide and one nitrogen atom of SCN⁻ ion. The structures of these compounds are dictated by the imidazolium cations.     

Hydrothermal syntheses and structures of the uranyl tellurates AgUO2(HTeO5) and Pb2UO2(TeO6)

Two uranyl tellurates, AgUO₂(HTeO₅) (1) and Pb₂UO₂(TeO₆) (2), were synthesized under hydrothermal conditions and were structurally, chemically, and spectroscopically characterized. 1 crystallizes in space group Pbca, a=7.085(2) Å, b=11.986(3) Å, c=13.913(4) Å, V=1181.5(5) Å³, Z=8; 2 is in P2(1)/c, a=5.742(1) Å, b=7.789(2) Å, c=7.928(2) Å, V=90.703(2) Å³, and Z=2. These are the first structures reported for uranyl compounds containing tellurate. The U⁶⁺ cations are present as (UO₂)²⁺ uranyl ions that are coordinated by O atoms to give pentagonal and square bipyramids in compounds 1 and 2, respectively. The structural unit in 1 is a sheet consisting of chains of edge-sharing uranyl pentagonal bipyramids that are one bipyramid wide, linked through the dimers of TeO₆ octahedra. In 2, uranyl square bipyramids share each of their equatorial vertices with different TeO₆ octahedra, giving a sheet with the autunite-type topology. Sheets in 1 and 2 are connected through the low-valence cations that are located in the interlayer region. The structures of 1 and 2 are compared to those of uranyl compounds containing octahedrally coordinated cations.     

Nickel(IV) dithiocarbamato complexes of the [Ni(ndtc)3]X type: X-ray structure of [Ni(hmidtc)3][FeCl4]

A series of fourteen octahedral nickel(IV) dithiocarbamato complexes of the general formula [Ni(ndtc)₃]X·yH₂O {ndtc stands for the appropriate dithiocarbamate anion, X stands for ClO₄⁻ (1-8; y = 0) or [FeCl₄]⁻ (9-14; y = 0 for 9-12, 1 for 13 and 0.5 for 14} was prepared by the oxidation of the corresponding nickel(II) complexes, i.e. [Ni(ndtc)₂], with NOClO₄ or FeCl₃. The complexes, involving a high-valent Ni^IVS₆ core, were characterized by elemental analysis (C, H, N, Cl and Ni), UV-Vis and FTIR spectroscopy, thermal analysis and magnetochemical and conductivity measurements. The X-ray structure of [Ni(hmidtc)₃][FeCl₄] (9) was determined {it consists of covalently discrete complex [Ni(hmidtc)₃]⁺ cations and [FeCl₄]⁻ anions} and this revealed slightly distorted octahedral and tetrahedral geometries within the complex cations, and anions, respectively. The Ni(IV) atom is six-coordinated by three bidentate S-donor hexamethyleneiminedithiocarbamate anions (hmidtc), with Ni-S bond lengths ranging from 2.2597(5) to 2.2652(5) Å, while the shortest Ni···Cl and Ni···Fe distances equal 4.1043(12), and 6.2862(6) Å, respectively. Moreover, the formal oxidation state of iron in [FeCl₄]⁻ as well as the coordination geometry in its vicinity was also proved by ⁵⁷Fe Mössbauer spectroscopy in the case of 9.     

Cation-anion interactions involving hydrogen bonds: Syntheses and crystal structures study of hexafluorotitanate(IV) salts with pyridine and methyl substituted pyridines

Fluorotitanates (LH)₂[TiF₆]·nH₂O (1: R = pyridine, n = 1, 2: R = 2-picoline, n = 2, 3: R = 2,6-lutidine, n = 0, 4: R = 2,4,6-collidine, n = 0) and (LH)[TiF₅(H₂O)] (3a: L = 2,6-lutidine) have been synthesized by the reaction of pyridine or corresponding methyl substituted pyridines and titanium dioxide dissolved in hydrofluoric acid. The crystal structures of ionic compounds 1, 2, 3, 3a and 4 have been determined by single-crystal X-ray diffraction analysis. The hydrogen bonding led to the formation of discrete (LH)₂[TiF₆] units (4), chains (1-3), and layers (3a). The additional π-π interactions present in 1, 2, and 4 results in chain structures of 1 and 4 and in a layer structure of 2. The [TiF₆]²⁻ and [TiF₅(H₂O)]⁻ anions were observed by ¹⁹F NMR spectroscopy in aqueous solutions of 1, 2, 3, 3a and 4.     

Hydrothermal synthesis and structures of two novel chain-like heteropolymolybdate formed by Keggin cluster units

Two novel heteropolymolybdate, [H₂bpy]₂ [Hbpy] [PCuMo₁₁O₃₉]·H₂O 1 and [H₂bpy]₂ [Hbpy] [PZnMo₁₁O₃₉]·2.75H₂O 2, have been prepared under mild hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. The two compounds are isostructural and crystallize in the monoclinic space group P2(1)/n (No. 14) with a=13.440(3) Å, b=26.660(5) Å, c=15.240(3) Å, β=99.55(3)°, and Z=4 for the compound 1, and a=13.610(3) Å, b=26.781(5) Å, c=15.205(3) Å, β=100.40(3)°, and Z=4 for the compound 2. Compound 1 and 2 exhibit a zigzag chain structure in which Keggin anions are connected through a common oxygen atom. They are the first characterized compounds containing 1D chains of transition-metal substituted Keggin heteropolymolybdate. Other characterizations by elemental analysis, IR, EPR, TG, and XRPD are also described.     

Aqueous syntheses of [(Cp-R)M(CO)3] type complexes (Cp = cyclopentadienyl, M = Mn, Tc, Re) with bioactive functionalities

We describe reactions of [^99mTc(H₂O)₃(CO)₃)]⁺ (1) with Diels-Alder products of cyclopentadiene such as “Thiele’s acid” (HCp-COOH)₂ (2) and derivatives thereof in which the corresponding [(Cp-COOH)^99mTc(CO)₃)] (3) complex did form in water. We propose a metal mediated Diels-Alder reaction mechanism. To show that this reaction was not limited to carboxylate groups, we synthesized conjugates of 2 (HCp-CONHR)₂ (4a-c) (4a, R = benzyl amine; 4b, R = N_α-Boc-l-2,3-diaminopropionic acid and 4c, R = glycine). The corresponding ^99mTc complexes [(4a)^99mTc(CO)₃)] 6a, [(4b)^99mTc(CO)₃)] 6b and [(4c)^99mTc(CO)₃)] 6c have been prepared along the same route as for Thiele’s acid in aqueous media demonstrating the general applicability of this synthetic strategy. The authenticity of the ^99mTc complexes on the no carrier added level have been confirmed by chromatographic comparison with the structurally characterized manganese or rhenium complexes.Studies of the reaction of 1 with Thiele’s acid bound to a solid phase resin demonstrated the formation of [(Cp-COOH)^99mTc(CO)₃)] 3 in a heterogeneous reaction. This is the first evidence for the formation of no carrier added ^99mTc radiopharmaceuticals containing cyclopentadienyl ligands via solid phase syntheses. Macroscopically, the manganese analogue 5a and the rhenium complexes 5b-c have been prepared and characterized by IR, NMR, ESI-MS and X-ray crystallography for 5a (monoclinic, P2₁/c, a = 9.8696(2) Å, b = 25.8533(4) Å, c = 11.8414(2) Å, β = 98.7322(17)°) in order to unambiguously assign the authenticity of the corresponding ^99mTc complexes.     

Mononuclear Fe(III) and tetranuclear [Fe(III)Gd(III)]2 complexes with a Schiff-base ligand derived from the o-vanillin: Synthesis, crystal structures and magnetic properties

The mononuclear high-spin iron(III) complexes [Fe(3-MeOsalpn)Cl(H₂O)] (1) and [Fe(3-MeOsalpn)(NCS)(H₂O)]·0.5CH₃CN (2) and the tetranuclear oxo-bridged compound [{Fe(3-MeOsalpn)Gd(NO₃)₃}₂(μ-O)]·CH₃CN (3) [3-MeOsalpn²⁻ = N,N′-propylenebis(3-methoxysalicylideneiminate)] have been prepared and magneto-structurally characterised. The iron(III) ion in 1 and 2 is six-coordinated in a somewhat distorted octahedral surrounding with the two phenolate-oxygens and two imine-nitrogens from the Schiff-base building the equatorial plane and a water (1 and 2) and a chloro (1)/thiocyanate-nitrogen (2) in the axial positions. The neutral mononuclear units of 1 and 2 are assembled into centrosymmetric dinuclear motifs through hydrogen bonds between the axially coordinated water molecule of one iron centre and methoxy-oxygen atoms from the Schiff-base of the adjacent iron atom. The values of the intradimer metal-metal distance within the supramolecular dimers are 4.930 (1) and 4.878 Å (2). The tetranuclear of 3 can be described as two {Fe^III(3-MeOsalpn)} units connected through an oxo-bridge, each one hosting a [Gd^III(NO₃)₃] entity in the outer cavity defined by the two phenolate- and two methoxy-oxygen atoms. The values of the intramolecular Fe?Fe and Fe?Gd distances in 3 are 3.502 and 3.606 Å, respectively. The analysis of the magnetic data of 1-3 in the temperature range 1.9-300 K shows the occurrence of weak intermolecular antiferromagnetic interactions in 1 and 2 [J = −0.76 (1) and −0.75 cm⁻¹ (2) with the Hamiltonian defined as H = −JS_Fe1·S_Fe1] whereas two intramolecular antiferromagnetic interactions coexist in 3, one very strong between the two iron(III) ions (J₁) through the oxo bridge and the other much weaker between the iron(III) and the Gd(III) ions (J₂) across the double phenoxo oxygens [J₁ = −275 cm⁻¹ and J₂ = −3.25 cm⁻¹, the Hamiltonian being defined as H=-J₁S_Fe1·S_Fe1^′-J₂(S_Fe1·S_Gd1+S_Fe1^′·S_Gd1^′)]. These values are analysed in the light of the structural data and compared with those of related systems.     

Synthesis, characterization, reactivity and computational studies of new rhenium(I) complexes with thiosemicarbazone ligands derived from 4-(methylthio)benzaldehyde

N-thioamide thiosemicarbazone derived from 4-(methylthio)benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in methanol gave the adducts [ReX(CO)₃(HLⁿ)] (1a X = Cl, n = 1; 1a′ X = Br, n = 1; 1b X = Cl, n = 2; 1b′ X = Br, n = 2; 1c X = Cl, n = 3; 1c′ X = Br, n = 3) in good yield.All the compounds have been characterized by elemental analysis, mass spectrometry (ESI), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³, HL³·(CH₃)₂SO and 1b′·H₂O were also elucidated by X-ray diffraction. In 1b′, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms (κS,N³) forming a five-membered chelate ring, as well as three carbonyl and bromide ligands. The resulting coordination polyhedron can be described as a distorted octahedron.The structure of the dimers is based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆] (2a), [Re₂(L²)₂(CO)₆] (2b) and [Re₂(L³)₂(CO)₆] (2c) as determined by X-ray studies. Methods of synthesis were optimized to obtain amounts of these thiosemicarbazonate complexes. In these compounds the dimer structures are achieved by Re-S-Re bridges, where S is the thiolate sulphur from a κS,N³-bidentate thiosemicarbazonate ligand.Some single crystals isolated in the synthesis of 2b contain [Re(L⁴)(L²)(CO)₃] (3b) where L⁴ (=2-methylamine-5-(para-methylsulfanephenyl)-1,3,4-thiadiazole) is originated in a cyclization process of the thiosemicarbazone. Furthermore, the rhenium atom is coordinate by the sulphur and the thioamidic nitrogen of the thiosemicarbazonate (κS,N²) affording a four-membered chelate ring.     

Novel hydridotris(pyrazolyl)borate ruthenium(II) complexes containing the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane: Synthesis and evaluation of DNA binding properties

A series of half-sandwich ruthenium(II) complexes containing κ³(N,N,N)-hydridotris(pyrazolyl)borate (κ³(N,N,N)-Tp) and the water-soluble phosphane 1,3,5-triaza-7-phosphaadamantane (PTA) [RuX{κ³(N,N,N)-Tp}(PPh₃)_2−n(PTA)_n] (n = 2, X = Cl (1), n = 1, X = Cl (2), I (3), NCS (4), H (5)) and [Ru{κ³(N,N,N)-Tp}(PPh₃)(PTA)L][PF₆] (L = NCMe (6), PTA (7)) have been synthesized. Complexes containing 1-methyl-3,5-diaza-1-azonia-7-phosphaadamantane(m-PTA) triflate [RuCl{κ³(N,N,N)-Tp}(m-PTA)₂][CF₃SO₃]₂ (8) and [RuX{κ³(N,N,N)-Tp}(PPh₃)(m-PTA)][CF₃SO₃] (X = Cl (9), H (10)) have been obtained by treatment, respectively, of complexes 1, 2 and 5 with methyl triflate. Single crystal X-ray diffraction analysis for complexes 1, 2 and 4 have been carried out. DNA binding properties by using a mobility shift assay and antimicrobial activity of selected complexes have been evaluated.     

Stereoselective synthesis of (E)-N,N-diethyl-3-(imidazo[1,2-a]pyrid-2-yl)-2-(phenylsulfonyl)propenamide

The title compound, gem-amidovinylsulfone 3, was synthesized stereoselectively by aldolic condensation of N,N-diethylphenylsulfonylacetamide 1 on imidazo[1,2-a]pyridine-2-carbaldehyde 2 adding Et₃N at the end. The X-ray crystal structure of 3 [C₂₀H₂₁N₃O₃S: M_r=383.5, monoclinic, P2₁, a=8.191(4) Å, b=21.132(2) Å, c=11.752(1) Å, β=96.40(2)°, V=2022(1) Å³, Z=4 (two molecules per asymmetric unit), D_calc=1.260 g cm⁻³, λ(Mo Kα)=0.71073 Å, μ=0.184 mm⁻¹, F(000)=808, T=293(2)K, R=0.059 for 5105 observed reflections with I≥2σ(I)] was determined, and confirmed the (E) configuration.     

Syntheses, structures and magnetic properties of two new one-dimensional cobalt (II) phosphites with organic amines acting as ligands

Two new one-dimensional (1D) inorganic-organic hybrid cobalt (II) phosphites Co(HPO₃) (py) (1) and [Co(OH)(py)₃][Co(py)₂][HPO₂(OH)]₃ (2) have been prepared under solvothermal conditions in the presence of pyridine (py). Compound 1 crystallizes in the monoclinic system, space group p2(1)/c, a=5.3577(7) Å, b=7.7503(10) Å, c=17.816(2) Å, β=94.327(2)°, V=737.67(16) Å³, Z=4. Compound 2 is orthorhombic, Cmcm, a=16.3252(18) Å, b=15.7005(16) Å, c=13.0440(13) Å, β=90.00° V=3343.4(6) Å³ and Z=4. Compound 1 possesses a 1D ladder-like framework constructed from CoO₃N tetrahedral, HPO₃ pseudo-pyramids and pyridine ligands. While compound 2 is an unusual inorganic-organic hybrid 1D chain, which consists of corner-shared six-membered rings made of CoO₃N₃/CoO₄N₂ octahedra and HPO₃ pseudo-pyramids through sharing vertices.     

Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

Mononuclear complexes of the type, M(CO)₄[Se₂P(OR)₂] (M = Mn, R = ⁱPr, 1a; Et, 1b; M = Re, R = ⁱPr, 3a; Et, 3b) can be prepared from either [-Se(Se)P(OⁱPr)₂]₂ (A) or [Se{-Se(Se)P(OEt)₂}₂] (B) with M(CO)₅Br. O,O′-dialkyl diselenophosphate ([(RO)₂PSe₂]^-, abbreviated as dsep) ligands generated from A and B act as a chelating ligand in these complexes. Upon refluxing in acetonitrile, these mononuclear complexes yield dinuclear complexes with a general formula of [M₂(CO)₆{Se₂P(OR)₂}₂] (M = Mn, R = ⁱPr, 2a; Et, 2b; M = Re, R = ⁱPr, 4a; Et, 4b). Dsep ligands display a triconnective, bimetallic bonding mode in the dinuclear compounds and this kind of connective pattern has never been identified in any phosphor-1,1-diselenoato metal complexes. Compounds 2b, 3b, and 4 are structurally characterized. Compounds 2b and 3b display weak, secondary Se?Se interactions in their lattices.     

Synthesis of dinitrosyl iron complexes (DNICs) with intramolecular hydrogen bonding

HSCH₂CONHCH₃ and HSCH₂CON(CH₃)₂ containing a peptide bond are prepared for the synthesis of DNICs with/without intra-molecular hydrogen bonding, respectively. The IR ν(NO) bands of [(NO)₂Fe(SCH₂CONHCH₃)₂]⁻ (2) appears at 1751, 1700 cm⁻¹. In complex 2, the presence of intramolecular [NH?S] hydrogen bonding was verified by the observation of IR spectroscopy with N−H stretching frequency 3334 cm⁻¹ (CDCl₃) and subsequently confirmed by single-crystal X-ray diffraction showing N−S distance of 2.94 Å. Complex 2 displays the rhombic EPR spectrum with g₁ = 2.039, g₂ = 2.031 and g₃ = 2.013 at in frozen H₂O. Complexes 2 and 3 rapidly release NO when exposed to light. The time needed for photolysis reactions of 2 is two times faster than that of 3 in less polar solvent. Representative time courses for the photolability of 2 and 3 in THF display the NO-off ability: 2 > 3.     

Syntheses and reactivities of azido coordinated CpCo(dithiolene) complexes

Azido coordinated dithiolene complexes [CpCo(N₃){S₂C₂(CO₂Me)₂}(S-CHR¹R²)], where R¹, R² = H (4a); R¹ = H, R² = SiMe₃ (4b); R¹ = H, R² = CO₂Et (4c), were synthesized by the reactions of the corresponding Cl⁻ coordinated precursors [CpCo(Cl){S₂C₂(CO₂Me)₂}(S-CHR¹R²)] (3a-3c) with sodium azide. The Cl⁻ coordinated complex 3d (R¹, R² = CO₂Me) did not produce any N₃⁻ coordinated complexes but formed the CR¹R²-bridged alkylidene adduct [CpCo{S₂C₂(CO₂Me)₂}(CR¹R²)] (2d; R¹, R² = CO₂Me). The structure of 4a was determined by X-ray diffraction study. In the molecular structure of 4a, the coordinated N₃⁻ ligand and CHR¹R² group were located at the same side with respect to the dithiolene ring (syn form), although the corresponding Cl⁻ precursor (3a; R¹, R² = H) was anti form. A structural conversion of syn/anti was conceivable during the Cl⁻/N₃⁻ ligand exchange. Thermal (80 °C) and photochemical reactions (Hg lamp) of 4a-4c were performed. Among them, 4c was relatively well reacted compared with the others to form the CR¹R²-bridged alkylidene adduct (2c; R¹ = H, R² = CO₂Et), followed by a formal HN₃ elimination, and the reaction also produced non-adduct of the cobalt dithiolene complex [CpCo{S₂C₂(CO₂Me)₂}] (1). The electrochemical 1e⁻ reduction of 4c underwent a formal N₃⁻ ligand elimination, and successive second reduction caused the CHR¹R² group elimination or reformed the CR¹R²-bridged alkylidene adduct 2c.     

Experimental and theoretical study of N-(2-hydroxyethyl)morpholine betaine

N-(2-hydroxyethyl)morpholine betaine (HEMB) has been characterized by a single crystal X-ray analysis, FTIR spectroscopy and DFT calculations. The crystals are monoclinic, space group P2₁/c with a=10.273(2), b=9.360(2), c=9.447(2) Å and β=104.72(3)Å. Two molecules of HEMB form a centrosymmetric dimer (X2) connected by a pair of hydrogen bonds between the CH₂CH₂OH and COO⁻ groups, with the O?O distance of 2.672(2) Å. The morpholine ring adopts a chair conformation with the CH₂CH₂OH group in the axial and the CH₂COO⁻ group in the equatorial position. The structures of the dimer, B2, and two monomers, B1a and B1b, have been optimized by the B3LYP approach using the 6-31G(d,p) basis set. The computed structure of B2, agrees well with the experimental X2. From two stable monomeric conformers the more favored is B1a, with the intramolecular hydrogen bond with the O-H?O distance of 2.566 Å. The effects of hydrogen bonding and electrostatic interactions on the conformation of the molecules investigated have been discussed. The FTIR spectrum shows a broad absorption in the 3300-2600 cm⁻¹ region, typical of moderate O-H?O hydrogen bonds.     

Extended chains via hydrogen bond linkages of dinuclear copper(II) and cadmium(II) complexes with a new flexible disulfoxide ligand

A new flexible disulfoxide ligand 1,6-bis(benzylsulfinyl)hexane (L), which is a mixture of the meso and rac isomers, was treated with Cu^II or Cd^II nitrate and obtained dimeric complex [Cu₂(L)₃(H₂O)₂(NO₃)₄] 2 or [Cd₂(L)₃(H₂O)₂(NO₃)₄] 3. In the reacting system the crystals of meso isomer 1 of L together with 2 or 3 were obtained. 2 and 3 have similar molecular structures. In the neutral dimer, three ligands present two kinds of coordination models: monodentate and bis-monodentate. The neutral dimeric units in 2 and 3 are linked by hydrogen bonds to yield a chain structure. Crystal structures of all three compounds were determined by single-crystal X-ray diffraction methods. Crystal data for 1: monoclinic, space group Cc, a=41.95(2), b=5.132(2), c=8.660(4) Å, β=94.898(9)°, V=1857.7(15) Å³, Z=4, final refinement (I>2σ(I)): R1=0.0659, wR2=0.1415. Crystal data for 2: triclinic, space group P-1, a=9.242(4), b=9.539(4), c=21.042(9) Å, α=83.888(9), β=87.971(8), γ=74.177(9)°, V=1774.6(13) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0577, wR2=0.0954. Crystal data for 3: triclinic, space group P-1, a=9.203(4), b=9.831(3), c=20.860(7) Å, α=84.313(6), β=86.432(7), γ=74.188(6)°, V=1805.9(11) Å³, Z=2, final refinement (I>2σ(I)): R1=0.0548, wR2=0.1192.     

Synthesis, structure of [H3dien]·(MF6)·H2O (M=Cr, Fe) and Fe Mössbauer study of [H3dien]·(FeF6)·H2O

Single crystals of [H₃dien]·(FeF₆)·H₂O (I) and [H₃dien]·(CrF₆)·H₂O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna2₁) with a=11.530(2) Å, b=6.6446(8) Å, c=13.787(3) Å, V=1056.3(2) Å³ and Z=4. II is monoclinic (P2₁/c) with a=13.706(1) Å, b=6.7606(6) Å, c=11.3181(9) Å, β=99.38(1)°, V=1034.7(1) Å³ and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R₁/wR₂ reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF₆ or CrF₆ octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by ⁵⁷Fe Mössbauer spectrometry: the hyperfine structure confirms the presence of Fe³⁺ in octahedral coordination and reveals the existence of paramagnetic spin fluctuations.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.