NMR Studies of Mixed-Ligand Lanthanide Complexes in Solution: Pseudorotation and Ring Inversion of 18-Crown-6 Molecule in Cerium Subgroup Chelates

¹H and ¹³C NMR measurements are reported for the CDCl₃ and CD₂Cl₂ solutions of [La(NO₃)₃(18-crown-6)] (I), [Pr(NO₃)₃(18-crown-6)] (II) and [Ce(NO₃)₃(18-crown-6)] (III) complexes. Temperature dependencies of the ¹H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH ^‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C ₂ symmetry axis, the second one with ΔH ^‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.This revised version was published online in July 2005 with a corrected issue number.     

NMR Studies of Mixed-Ligand Lanthanide Complexes in Solution: Pseudorotation and Ring Inversion of 18-Crown-6 Molecule in Cerium Subgroup Chelates

¹H and ¹³C NMR measurements are reported for the CDCl₃ and CD₂Cl₂ solutions of [La(NO₃)₃(18-crown-6)] (I), [Pr(NO₃)₃(18-crown-6)] (II) and [Ce(NO₃)₃(18-crown-6)] (III) complexes. Temperature dependencies of the ¹H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH ^‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C ₂ symmetry axis, the second one with ΔH ^‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.     

(18-Crown-6)(nitrato-<Emphasis Type="Italic">O,O</Emphasis>′)potassium and (18-crown-6)(nitrato-O,O′)potassium<Subscript>(0.91)</Subscript>silver<Subscript>(0.09)</Subscript>: Synthesis and crystal structures

Two complexes with similar compositions are synthesized: (18-crown-6)(nitrato-O,O′)potassium (I) and (18-crown-6)(nitrato-O,O′)potassium_(0.91)silver_(0.09) (II). Their isomorphic orthorhombic crystals (space group P2₁2₁2₁, Z = 4) are studied by X-ray diffraction analysis. Structure I (a = 8.553 Å, b = 11.967 Å, c = 17.871 Å) and structure II (a = 8.540 Å, b = 11.956 Å, c = 17.867 Å) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.044 (I) and 0.055 (II) for all 2385 (I) and 2379 (II) measured independent reflections. Complex molecules [K(NO₃)(18-crown-6)] in structure I and [K_0.91Ag_0.09(NO₃)(18-crown-6)] in compound II are of the host-guest type and rather similar in structure. Their 18-crown-6 and NO ₃ ^? ligands are disordered over two orientations. The K⁺ cation in complex I and the mixed cation (K_0.91Ag_0.09)⁺ in complex II reside in the cavity of the disordered 18-crown-6 ligand and is coordinated by its six O atoms and by two disordered O atoms of the NO ₃ ^? . ligand. The coordination polyhedron (CN = 8) of the K⁺ cation in complex I and that of (K_0.91Ag_0.09)⁺ cation in complex II is a distorted hexagonal pyramid with a base of six O atoms of the 18-crown-6 ligand and a split vertex at two O atoms of the NO ₃ ^? ligand.     

Stability and structure in solution of potassium and barium complexes with N,N’-diaryldiaza-18-crown-6: Crystal structure of N,N’-Bis(4-dimethylaminophenyl)diaza-18-crown-6 and its complex with barium perchlorate

It has been shown that N,N’-diaryldiaza-18-crown-6 ethers with p-dimethylamino-and p-methoxy groups in the benzene ring (aryl is 4-Mc₂NC₆H₄) (I) and 4-MeOC₆H₄ (II) form complexes with potassium and barium salts. The influence of these salts on the UV and ¹H NMR spectra of crown ethers I and II has been studied. The stability constants (logβ) of the complexes increase in the series II · Ba(ClO₄)₂ (2.0), I · Ba(ClO₄)₂ (2.3), II · KBr (2.8), I · KBr (3.0). N,N’-bis(4-dimethylphenylamine)diaza-18-crown-6 (L, I) and its complex with barium perchlorate Ba(ClO₄)₂ · L (III) are characterized by X-ray crystallography. The crystals of I are monoclinic: a = 13.778(2) Å, b = 5.9731(9) Å, c = 17.542(3) Å, β = 106.65(1)°, V = 1383.1(4) ų, Z = 2, space group P2₁/n, R = 0.0374 for 990 reflections with I > 2σ(I). The crystals of III are monoclinic: a = 17.275(4) Å, b = 8.017(2) Å, c = 26.935(4) Å, β = 100.47(2)°, V = 3669(1) ų, Z = 4, space group C2/c, R = 0.0320 for 1897 reflections with I > 2σ(I). The molecules of I and III are centrosymmetric. In III, the Ba atom is in the center of substituted diaza-18-crown-6 (DA18C6). The Ba atom is coordinated by all six donor atoms of diaza-18-crown-6 (av. Ba-O, 2.779(3) Å; Ba-N, 3.004(4) Å) and four oxygen atoms of two asymmetrically bound perchlorate groups (Ba-O, 2.832(4) and 3.031(4) Å) arranged below and above the plane of substituted diaza-18-crown-6. The conformations of the macrocycle in free and coordinated L are different.     

(18-Crown-6)sodium tribromide and (18-crown-6)potassium triiodide (with an admixture of bromodiiodide): Synthesis and crystal structure

Two crystalline host-guest complexes are synthesized and studied using X-ray diffraction analysis: (18-crown-6)sodium tribromide [Na(18-crown-6)]⁺ · Br ₃ ^? (I) and (18-crown-6)potassium tribromide (with an admixture of bromodiiodide) [K(18-crown-6)]⁺ · (Br_0.25I_2.75)^? (II). The structures of compound I (space group P2₁/_{n, a} = 8.957 Å, b = 8.288 Å, c = 14.054 Å, β = 104.80°, Z = 2) and compound II (space group Cc, a = 8.417 Å, b = 15.147 Å, c = 17.445 Å, β = 99.01°, Z = 4) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.098 (I) and 0.036 (II) for all 2311 (I) and 2678 (II) independent measured reflections on a CAD-4 automated diffractometer (λMoK _α). Similar crystalline complexes I and II exist as infinite chains of alternating complex cations and trihalide anions linked to each other through weak Na-Br or K-I coordination bonds. In [Na(18-crown-6)]⁺ and [K(18-crown-6)]⁺ complex cations, the Na⁺ or K⁺ cation (coordination number is eight) is located in the center of the cavity of the 18-crown-6 ligand and coordinated by the six O atoms and two terminal Br or I atoms of two trihalide anions lying on opposite sides of the rms plane of the crown ligand.     

Paramagnetic properties and molecular structure of coordination saturated inclusive lanthanide complexes with 18-crown-6 using NMR

Earlier NMR spectra of lanthanide complexes [Ln(18-crown-6)(NO₃)₃] have been analyzed by us (Babailov in Inorg Chem 51(3):1427–1433, 2012), where Ln³⁺ = La³⁺ (I), Ce³⁺ (II), Pr³⁺ (III) and Nd³⁺ (IV). The NMR signal assignment and conformational molecular dynamic have been found by 1D NOE and relaxation spectroscopy as well as on 2D NOESY and EXSY experiments at 170 K. In the present paper the ¹H NMR method is used to study the features of paramagnetic properties of complexes I–IV and [Eu(18-crown-6)(NO₃)₃] (V) at ambient temperature. The investigation was carried out by special method based on analysis of Δδ/z> on k(Ln)/z> (where k(Ln) is Bleaney’s constant, Δδ is paramagnetic contribution to the lanthanide-induced shifts). The obtained results indicate that the structure of the complexes (in CDCl₃ and CD₂Cl₂) are very similar.     

(18-Crown-6)potassium tetrachloroferrate(III), dibromodichloroferrate(III), and tetrabromoferrate(III): Synthesis and crystal structures

Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]^?(I), [FeBr₂Cl₂]^? (II), and [FeBr₄]^? (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd $ \bar 3 Three new crystalline complexes are synthesized: [K(18-crown-6)]⁺ · An, where An = [FeCl₄]⁻(I), [FeBr₂Cl₂]⁻ (II), and [FeBr₄]⁻ (III). The crystals of compounds I–III are cubic and isomorphic, space group Fd (Z = 16): a = 20.770(2) ? for I, 20.844(3) ? for II, and 20.878(4) ? for III. Structures I–III are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.047 (I), 0.059 (II), and 0.098 (III) for all 680 (I), 684 (II), and 686 (III) independent reflections. In two tetrahedral anions [Fe(1)X₄]⁻ and [Fe(2)X₄]⁻ in structures I–III, all halogen atoms (X = Cl and Br) are randomly disordered over three close positions relative to the crystallographic axes 3. Structures I–III contain the [K(18-crown-6)]⁺ host-quest complex cation. The K⁺ cation (CN = 8) resides in the cavity of the 18-crown-6 ligand and coordinated by its six O atoms and two disordered halogen X atoms. The coordination polyhedron of the K⁺ cation in complexes I–III is a distorted hexagonal bipyramid. Original Russian Text ? A.N. Chekhlov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1566–1570.     

One-dimensional Chain Crown Ether Complexes. Synthesis and Crystal Structure of Benzo-18-Crown 6 Complexes with Na 2 [M(SCN) 4 ] (M = Pd, Pt)

Two benzo-18-crown-6 (B18-C-6) complexes: [Na(B18-C-6)]₂[Pd(SCN)₄](H₂O)({bf 1}) and [Na(B18-C-6)]₂[Pt(SCN)₄]...0.5C₂H₄C1₂ (2)have been synthesized and characterized by elemental analysis, IR spectrum and X-raydiffraction analysis. The crystal of complex 1 belongs to monoclinic, space group P2₁/n with cell dimensions, a = 1.0481(3), b = 1.2864 (3), c = 1.7003 (4) nm, = 93.626(4)°, V = 2.2879 (9) nm³, Z = 2, D_calcd = 1.491 g/cm³, F(000) = 1060, R₁ = 0.0562, wR₂ = 0.1412 and 2 is triclinic, spacegroup P1 with cell dimensions, a = 0.9581(3), b = 1.2173 (3), = 2.1198 (6) nm, = 79.522(4), = 77.911(4), = 78.617(4)°, V = 2.3442(11) nm³ Z = 2, D_calcd = 1.626 g/cm³, F(000) = 1154, R₁ = 0.0515, wR₂ = 0.0612.Two complexes show one-dimensional chain of [Na(B18-C-6)]⁺ complex cations and [M(SCN)₄]^2- (M = Pd, Pt) complex anion bridged by Na–O–Na interactions of H₂O molecule or Na-O bond of B18-C-6 between adjacent [Na(B18-C-6)]⁺ units respectively.     

Thermodynamics of cesium complexes formation with 18-crown-6 in ionic liquids

Thermodynamic data for cesium complexes formation with 18-crown-6 (18C6, L) [Cs(18C6)]⁺ in N-butyl-4-methyl-pyridinium tetrafluoroborate ([BMPy][BF₄], I), in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄], II) and in 1-butyl-3-methylimidazolium dicyanamide ([BMIM][N(CN)₂], III) were measured with NMR ¹³³Cs technique at 23–50 °C. The stability of cesium complex in RTILs is estimated to be in the range between water and DMFA. Stability constants for [Cs(18C6)]⁺ are found to decrease as temperature is increasing. The following values for lgK(Cs+L) and ΔH(Cs+L) at 23 °C are determined: 2.6 (0.3), ?47(1) kJ/mol (RTIL I); 2.8(0.3), ?80(3) kJ/mol (RTIL II) and 3.03 (0.08), ?47(2) kJ/mol (RTIL III). It is demonstrated that enthalpy change promotes complex formation while the corresponding change of entropy is negative and provides decomposition of [Cs(18C6)]⁺.     

Spin exchange between transition metal complexes and nitroxyl radicals in nonaqueous media

New complexes of diaza- and tetraaza-containing crown ethers, viz., 1,10-diaza-18-crown-6 (1), 1,4,8,12-tetraazacyclopentadecane (2), 1,4,8,11-tetraazacyclotetradecane (3), and 1,4,8,11-tetraazacyclotetradecane 1,4,8,11-tetrachloride tetraacetic acid tetrahydrate (4), with the divalent copper and nickel ions and the Cl^–, Br^–, ClO₄ ^–, NO₃ ^–, and AcO^– counterions were synthesized. The exchange interactions of these compounds and paramagnetic copper and nickel salts with the TEMPO radical in MeOH—CHCl₃ binary mixtures of different compositions were studied. The plots of the linewidths of the hyperfine coupling components of TEMPO vs. concentration of the ions and temperature show that the frequency of diffusion collisions is the rate-limiting step for spin exchange (strong exchange regime). A strong dependence of the exchange rate constant (k _ex) on the crown ether and counterion structure was found. The isotropic hyperfine coupling constants (a _Cu) and g factors (g _i ) were measured for the Cu^II complexes with the crown ethers. In the case of the crown ether complexes 1—3 with CuCl₂, the a _Cu constant decreases linearly with an increase in g _i = g _i – 2.0023 in the series 3 < 2 < 1, whereas k _ex increases linearly in the same series with a decrease in the contact HFC on the Cu^II nucleus (K) and a decrease in covalence of bonding. For the complexes of 2 with Cu^II and different axial ligands (counterions), k _ex increases in the series Cl^– < ClO₄ ^– AcO^– Br^–; < NO₃ ^–. In the case of the complexes of 2 with NiCl₂, k _ex increases in the series 1 < 4 < 3 2. For the Cu^II and Ni^II salts with the Cl^–, ClO₄ ^–, and NO₃ ^– anions, the k _ex values are almost independent of the anion nature. The correlation of the k _ex values with the electron-spin parameters of the complexes is discussed.     

Magnetic properties of biacetyldihydrazone complexes

Summary Magnetic susceptibilities of the biacetyldihydrazone (BdH) complexes [M(BdH)₃](NO₃)₂ (M = Co^II, Ni^II, Cu^II or Zn^II), [Fe(BdH)₃](NO₃)₃, [M(BdH)₃](Ni(dto)₂] (M = Co^II, Ni^II or Zn^II; dto = dithiooxalate), [(BdH)₂Cu(dto)Ni(dto)] and [Fe(BdH)₃]₂[Ni(dto)₂]₃ have been studied in the 4.2–295 K range. Zn^II complexes are diamagnetic, and complexes of Ni^II, Cu^II and Fe^III obey the Curie-Weiss law. The Co^II complexes behave anomalously and the results are interpreted in terms of a high spinlow spin equilibrium.     

Crystal Structure of 1,10-Diazonia-18-crown-6 Bis(hydrogen oxalate) and 1,10-Diazonia-18-crown-6 Oxalate Dihydrate

An X-ray diffraction study has been performed to study the crystal structure of 1,10-diazonia-18-crown-6 bis(hydrogen oxalate) [H₂DA18C6]²⁺·2C₂HO ₄ ^- (I) and 1,10-diazonia-18-crown-6 oxalate dihydrate [H₂DA18C6]²⁺·2C₂O ₄ ^- ·2H₂O (II). Crystals I are triclinic: space group , a = 7.825, b = 7.861, c = 9.349 , = 97.28, = 110.22, = 99.12°, Z = 1. Crystals II are monoclinic: space group P2 ₁ /n, a = 8.783, b = 10.640, c = 10.225 , = 97.04°, Z = 2. The structures of I and II were solved by direct methods and refined by the full-matrix least-squares procedure anisotropically to R = 0.036 (I) and 0.042 (II) for all 2206 (I) and 1990 (II) unique reflections measured (CAD-4 automatic diffractometer, CuK ). In the crystal structures, the ionic complexes (salts) I and II are not individual guest–host complex molecules but are parts of complex (infinite in two directions) three-dimensional layers of H-bonded molecular anions and DA18C6 dications (and water molecules in II). In structures I and II, the centrosymmetric DA18C6 dications have different conformations: two-angle in I and four-angle in II. The unusual four-angle conformation of the DA18C6 dication was found for the first time.     

Interaction of uranyl monoaquadiformate with diaza-18-crown-6 in aqueous ethanol

The reaction of {[UO₂(HCOO)₂(H₂O)]} with diaza-18-crown-6 (DA18C6 = C₁₂H₂₆O₄N₂) in aqueous ethanol in the presence of formic acid yields the complexes {[DA18C6H₂]·[UO₂(HCOO)₃]₂} (I), [DA18C6H₂]·[UO₂(HCOO)₄] (II), and [DA18C6H₂]·(HCOO)₂·(H₂O)₂ (III). The complexes are characterized using IR spectroscopy, chemical analysis, and powder X-ray diffraction. From the comparison of the structural and spectral characteristics of [DA18C6H₂]·An₂·(H₂O)_2n (where An = Cl^?,NO ₃ ^? ,HCOO^?,HSO ₄ ^? ; n = 0.1), correlations are derived between the conformation of the [DA18C6H₂]²⁺ units and the conformation-sensitive frequencies. On the basis of these correlations, the conformations of the N⁺CCO and OCCO units were determined in the diazonia cations of compounds I and II and in [DA18C6H₂]·[UO₂(NO₃)₄]; the latter was prepared previously by reacting [UO₂(NO₃)₂(H₂O)₂]·(H₂O)₄ with DA18C6 in ethanol in the presence of nitric acid.     

(Mesitylene)ruthenium π-complexes with benzo-15-crown-5 and dibenzo-18-crown-6

The reactions of benzo-15-crown-5 and dibenzo-18-crown-6 with 1 equiv. of [(mes)Ru(MeNO₂)₃]²⁺ (mes = 1,3,5-C₆H₃Me₃) give the mononuclear complexes [(mes)Ru(η⁶-benzo-15-crown-5)]²⁺ (1) and [(mes)Ru(η⁶-dibenzo-18-crown-6)]²⁺ (2) in 50% yield. Similar reaction with 2 equiv. of [(mes)Ru(MeNO₂)₃]²⁺ produces the dinuclear complex [(μ-η⁶:η⁶-dibenzo-18-crown-6)Ru₂(mes)₂]⁴⁺ (3) in 96% yield as a 2:3 mixture of cis- and trans-isomers. Structures of 2(OTf)₂ and trans-3(OTf)₄ were confirmed by X-ray diffraction. The NMR titration showed that mononuclear dications 1 and 2 bind Na⁺ ion less effective (K_a = 600 and 250 M^-1) than free benzo-15-crown-5 and dibenzo-18-crown-6 (K_a = 2 × 10⁵ and 5 × 10⁶ M⁻¹). The dinuclear tetracation 3 does not bind Na⁺ within measurable limits of NMR titration method. The electrochemical behaviour of complexes 1-3 was studied in propylene carbonate solution. They exhibit a partially chemically reversible Ru(II)/Ru(I) reduction, which in the case of the dinuclear complex 3 proceeds through two slightly separated steps. The redox activity of the complexes is substantially unaffected by the presence of sodium ion.     

Crystal and molecular structure of (NH4)2[UO2(NO3)4] and [(NH4)(18C6)]2[UO2(NO3)4]

Single crystals of diammonium tetranitratouranylate (NH₄)₂[UO₂(NO₃)₄] (I) and a new diammonium tetranitratouranylate complex with 18-crown-6 [(NH₄)(18C6)]₂[UO₂(NO₃)₄] (II) have been synthesized by the reaction of diaquadinitratouranyl tetrahydrate with ammonium nitrate in a nitric acid solution and the reaction of the same reagents with 18C6 in an ethanol solution, respectively. The X-ray diffraction analysis of compounds I and II has been performed. Crystals of compounds I and II are monoclinic, Z = 2, space group P2₁/n, a = 6.4075(5) ?, b = 7.7851(7) ?, c = 12.4461(12) ?, β = 101.239(1)°, V = 608. 94(9) ?³ for compound I and a = 10.542(9) ?, b = 8.590(8) ?, c = 22.5019(19) ?, β = 101.632(1)°, V = 2058.3(3) ?³ for compound II. The [UO₂(NO₃)₄]²⁻ complex anion in compounds I and II contains two monodentate and two bidentate cyclic nitrato groups, and the coordination number of uranyl is 6. The 18C6 molecule in the structure of compound II has the classic crown conformation and combined with the ammonium ion by three hydrogen bonds. Compounds I and II formed by electrostatic attraction forces between counterions are stabilized by (NH₄⁺)NH...O(NO₃⁻) interionic hydrogen bonds.     

Diaquabromo(18-crown-6)rubidium and triaqua(18-crown-6)barium dibromide monohydrate: Synthesis and crystal structures

Two complexes are synthesized: diaquabromo(18-crown-6)rubidium [RbBr(18-crown-6)(H₂O)₂] (I) and triaqua(18-crown-6)barium dibromide monohydrate [Ba(18-crown-6)(H₂O)₃]²⁺ 2Br^? · H₂O (II). The orthorhombic structure of compound I (space group Pnma, a = 10.124 Å, b = 15.205 Å, c = 12.544 Å, Z = 4) and the monoclinic structure of compound II (space group C 2/c, a = 17.910 Å, b = 10.315 Å, c = 14.879 Å, β = 123.23°, Z = 4) are determined by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.063 (I) and 0.042 (II) for all 2293 (I) and 3363 (II) independent measured reflections (CAD-4 automated diffractometer, λMoK _α). The complex molecule [RbBr(18-crown-6)(H₂O)₂] in compound I and the randomly disordered cation [Ba(18-crown-6)(H₂O)₃]²⁺ in compound II are of the host-guest type: their Rb⁺ or Ba²⁺ cation (its coordination number is nine) is located in the cavity of the 18-crown-6 ligand and coordinated by all six O atoms. In structure I, the coordination polyhedron of Rb⁺ is a distorted hexagonal pyramid with a triple apex at the Br^? ligand and two O atoms of the water molecules. In structure II, the Ba²⁺ polyhedron is a distorted hexagonal bipyramid with one apex at the O atom of the water molecule and the other split apex at two O atoms of water molecules.     

Synthesis, structures, and thermolysis of new heterometallic cobalt, nickel, and copper complexes with the [Ru(NO)(NO2)4(OH)]2− anion as a ligand

Heterometallic complexes with pyridine-N-oxide (PyO), Ru(NO)(NO₂)₄(OH)Ni(PyO)₂(H₂O)] · CH₃COCH₃ (I), [{Ru(NO)(NO₂)₂(μ-NO₂)₂(μ-OH)Co}₂(μ-PyO)] · H₂O · CH₃COCH (II), and [Ru(NO)(NO₂)₄(OH)Cu(PyO)₂ (III), are isolated in the reactions of Na₂[Ru(NO)(NO₂)₄(OH)] with nitrates of the corresponding metals in the presence of the organic ligand. The compounds synthesized are characterized by IR spectra, thermal analysis, and X-ray diffraction analysis. Depending on the M²⁺ cation, the ruthenium cation is coordinated through the bidentate (III, Cu²⁺) or tridentate (I, Ni²⁺ and II, CO₂₊) mode involving the bridging OH group and one or two NO₂ groups. The thermal decomposition of complex II results in the formation of a Co_0.5Ru_0.5 solid solution, which is thermodynamically stable under the decomposition conditions. The thermolysis of complexes I and III in a hydrogen atmosphere leads to the formation of metastable solid solutions.     

Clathrate formation and phase equilibria in the pyridine-cadmium nitrate system

Preparative, thermal (DTA, TGA), solubility, strain and spectral (Raman) techniques were used to study clathrate and complex formation in the pyridine (Py)-cadmium nitrate system. Three compounds have been isolated and studied: the clathrate compound [CdPy₄(NO₃)₂] · 2Py (I), the complex [CdPy₃(NO₃)₂] (II) and a compound of composition Cd(NO₃)₂·7/4Py (III), of unknown nature. The phase diagram of the system has been determined for the concentration and temperature range 0–66 mass-% Cd(NO₃)₂ and –100 to +200 °C, respectively. ClathrateI undergoes polymorphous conversion at –51.8(4) °C and melts incongruently at 106.0(5) °C, forming complexII. CompoundsII andIII melt congruently at 165.5(4) and 191(1) °C, respectively. The complexes [CdPy₄(NO₃)₂] (the host phase) and [CdPy₂(NO₃)₂] are not observed in the system. The nature and thermodynamic parameters of the dissociation of clathrate I have been determined. For the process 1/13[CdPy₄)NO₃)₂] · 2Py_solid = 1/3[CdPy₃(NO₃)₂]_solid + Py_gas in the range 290–360K H ^o = 54.9(3) kj/mole, S ₂₉₈ ^o = 142(1) J/(mole K), G ₂₉₈ ^o = 12.5(5) kJ/mole.     

NLO active CuII/RuII and CdII/RuII coordination-organometallic complexes: synthesis,structural characterization and photoluminescence properties

Cu^II/Ru^II and Cd^II/Ru^II hybrid complexes [Cu(L_1–3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1a-3a) and [Cd(L_1-3)(NC₅H₄C≡CRu(dppe)₂Cl)] (1b–3b) have been prepared by reaction of trans-[RuCl(dppe)₂(C≡C-py-3)] (1) with copper or cadmium acetate in the presence of Schiff base ligands L_H1–3 (where L_H = 2-(pyrrole-2-yl-methylidine)aminophenol (L_H1), 5-bromo-2-(pyrrole-2-yl-methylidine)aminophenol (L_H2) and 5-nitro-2-(pyrrole-2-yl-methylidine)aminophenol (L_H3)). The hybrid materials were characterized on the basis of elemental analyses, TEM, IR, UV–visible, ¹H NMR, and ³¹P NMR spectral studies. TEM overview observations revealed well-dispersed spherical nanoparticles of ~60 nm are formed. Quasireversible redox behavior is observed for Cu^II/Ru^II complexes corresponding to Cu^I/Cu^II and Ru^II/Ru^III couples. All the complexes exhibit blue-green emission as a result of fluorescence from the intraligand (π → π*) emission excited state with good quantum yield. The second-order nonlinear optical (NLO) properties of Cu^II/Ru^II and Cd^II/Ru^II complexes have been investigated by the Kurtz-powder method. The second harmonic generation efficiency of these complexes show that these complexes are NLO active and display good second-order nonlinear optical activity.     

(18-Crown-6)potassium 0.84(diiodobromide) 0.16(dibromoiodide) and diaqua(18-Crown-6)chlororubidium: Syntheses and crystal structures

New host-guest compounds are synthesized and studied by X-ray diffraction analysis: (18-crown-6) potassium 0.84(diiodobromide) 0.16(dibromoiodide), [K(18-crown-6)]⁺ · (Br_1.16I_1.84)⁻, (I) and diaqua (18-crown-6)chlororubidium, [RbCl(18-crown-6)(H₂O)₂], (II). The crystals of compound I are monoclinic (space group P2₁/n, a = 9.157 ?, b = 8.589 ?, c = 14.072 ?, β = 102.27°, Z = 2). The structure of compound II is orthorhombic (space group Pnma, a = 9.813 ?, b = 15.231 ?, c = 12.629 ?, Z = 4). The structures are solved by a direct method and refined by the full-matrix anisotropic least squares to R = 0.062 (I) and 0.079 (II) for 3149 (I) and 2840 (II) independent reflections (CAD-4 automated diffractometer, λMoK _α radiation). The crystal structures of compounds I and II are different: compound I is built of infinite chains of the alternating cations [K(18-crown-6)]⁺ and mixed halide anions linked by weak coordination bonds K-Br or K-I, whereas individual molecules [RbCl(18-crown-6)(H₂O)₂] form structure II. Original Russian Text ? A.N. Chekhlov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1385–1391.