Syntheses and spectroscopic and structural characterization of silver(I) complexes containing tris(isobutyl)phosphine and poly(azol-1-yl)borates

Silver(I) derivatives [Ag(L)(PⁱBu₃)] (L = H₂B(tz)₂ (dihydrobis(1H-1,2,4-triazol-1-yl)borate), HB(tz)₃ (hydrotris(1H-1,2,4-triazol-1-yl)borate), Tp (hydrotris(1H-pyrazol-1-yl)borate), Tp∗ (hydrotris(3,5-dimethyl-1H-pyrazol-1-yl)borate), Tp^Me (hydrotris(3-methyl-1H-pyrazol-1-yl)borate), Tp^CF3 (hydrotris(3-trifluoromethyl-1H-pyrazol-1-yl)borate), Tp^4Br (hydrotris(4-bromo-1H-pyrazol-1-yl)borate), HB(btz)₃ (hydrotris(1H-1,2,4-benzotriazol-1-yl)borate), Tm (hydrotris(3-methy-1-imidazolyl-2-thione)borate), pzTp (tetrakis(1H-pyrazol-1-yl)borate), pz⁰Tp^Me (tetrakis(3-methyl-1H-pyrazol-1-yl)borate) have been synthesized from the reaction of [Ag(NO₃)(PⁱBu₃)₂] with ML (M = Na or K) and characterized both in solution (¹H- and ³¹P{¹H} NMR, ESI MS spectroscopy, conductivity) and in the solid state (IR, single crystal X-ray structure analysis). These complexes are air-stable and light-sensitive and non-electrolytes in CH₂Cl₂ and acetone in which they slowly decompose, even with the strict exclusion of oxygen and light, yielding metallic silver and/or azolate (Az) species of formula [Ag(Az)(PⁱBu₃)_x] upon breaking of the bridging B-N_(azole) bond. The solid state structures of [Ag(Tp)(PⁱBu₃)], [Ag(Tp^Me)(PⁱBu₃)], [Ag(Tp^CF3)(PⁱBu₃)], [Ag{HB(btz)₃}(PⁱBu₃)], and [Ag(Tm)(PⁱBu₃)] show that the silver atom adopts a distorted tetrahedral coordination geometry. [Ag(L)(PPh₃)] can be easily obtained from the reaction of [Ag(L)(PⁱBu₃)] with excess PPh₃, whereas from the reverse reaction of [Ag(L)(PPh₃)] with PⁱBu₃a mixture of [Ag(L)(PⁱBu₃)] and [Ag(L)]₂ and [Ag(L)(PPh₃)] was recovered. ³¹P{¹H} NMR variable temperature NMR studies showed that in the pz⁰Tp^x derivatives the scorpionate ligand acts as a bidentate donor, whereas tridentate coordination is found for all tris(azolyl)borate derivatives, both in solution and in the solid state. ESI MS data suggest the existence in solution of species such as [Ag(PⁱBu₃)₂]⁺ upon dissociation of the L ligand, and also the formation of dimeric species of the form [Ag₂(L)(PⁱBu₃)₂]⁺.     

Synthesis and physico-chemical studies of bimetallic alkoxy derivatives of chromium(III) with niobium(V) and tantalum(V)

Reactions of CrCl₃·3thf with KM(OPrⁱ)₆ in 1:3 molar ratios in benzene yield soluble complexes of the type Cr[M(OPrⁱ)₆]₃ (M=Nb or Ta). On heating under vacuum, these complexes tend to disproportionate into Cr(OPrⁱ)₃ and M(OPrⁱ)₅ (M=Nb or Ta). A number of bimetallic alkoxides have also been synthesized by the alcoholysis of Cr[M(OPrⁱ)₆]₃ with alcohols (methanol, ethanol and t-amyl alcohol). The IR, visible, electron spin resonance and magnetic properties of these newly synthesized complexes throw light on the structural features.     

The preparation and structure of tris[bis(pyrazolyl)borate]indium(III)

The compound In[(pz)₂BH₂]₃ (pz = 1-pyrazolyl, C₃H₃N₂⁻) was prepared from In(NO³)₃ and K[(pz)₂-BH₂] in water, and characterised by spectroscopic and X-ray methods. Crystals are orthorhombic,Pna2₁,a = 20.279(4),b = 8.884(2),c = 13.411(2)Å;R = 0.0285. Individual molecules contain a near-regular six-coordinate indium atom with In–N (av.) 2.241(5)Å. The pyrazolyl borate ligands are puckered, with dihedral angles between the two rings of each ligand in the range 133–144°.     

A study of some solvolysis reactions of bis(trimethylamine)chromium(III) chloride

Two competing reactions are present when benzene solutions of the five co-ordinate complex CrCl₃·2NMe₃ are treated with donor molecules viz., a) ligand substitution via solvolysis of metal-nitrogen bonds and b) the independent decomposition of the bis-trimethylamine adduct into tri-μ-chloro-trichlorotris(trimethylamine) dichromium(III), Cr₂Cl₆(NMe₃)₃, and trimethylamine. For all but very feeble donors reaction a) predominates and in the ensuing adduct formation the chromium(III) ions assume hexacoordination, e.g. pyridine and tetrahydrofuran react immediately to give the corresponding CrCl₃·3L complexes. Reaction b) shows second order kinetics with a rate constant k = 0.160 1 mole⁻¹ sec⁻¹ The spectral and magnetic properties of the binuclear compound Cr₂Cl₆(NMe₃)₃ have been interpreted in terms of adjacent six co-ordinate metal atoms and a proposed structure is based on two fused octahedra sharing a common trigonal face. The product obtained on treatment of CrCl₃·2NMe₃ with AgClO₄ involves only bidentate (C_2v) perchlorate ions as co-ordinated ligand and is formulated as Cr(ClO₄)₃.     

Poly(1,2,3-benzotriazolyl)borate complexes with copper(I) and tri-organophosphane: an unprecedented κ-coordination of [H2B(btz)2] (btz=1,2,3-benzotriazolyl) in the X-ray crystal structure of [Cu(PBn3)2{(btz)BH2(btz)}]

New copper(I) triorganophosphane derivatives [Cu(PR₃)_n{H₂B(btz)₂}] and [Cu(PR₃)_n{HB(btz)₃}] (n=1 or 2) have been synthesized from the reaction of CuCl with PR₃ (R=phenyl, cyclohexyl, benzyl, o-, m-, or p-tolyl) or PMePh₂ and potassium dihydrobis(1,2,3-benzotriazolyl)borate K[H₂B(btz)₂] or potassium hydrotris(1,2,3-benzotriazolyl)borate K[HB(btz)₃]. The complexes obtained have been characterized by elemental analyses and FT-IR in the solid state and by NMR (¹H and ³¹P{¹H}) spectroscopy and conductivity measurements in solution. Solution data are consistent with partial dissociation of complexes occurring throughout breaking of the CuP bond. Single crystal structural characterizations were undertaken for two of them. The structurally authenticated arrays are, (a) [Cu(PBn₃)₂{(btz)BH₂(btz)}] with a three coordinate P₂Cu(N) coordination sphere and the donor [H₂B(btz)₂] coordinated throughout only one N3 atom. (b) [Cu(P-m-tolyl₃)_n{(btz)₃BH}] with a four coordinate PCuN₃ coordination sphere with the tris(benzotriazolyl)borate acting as tripodal donor throughout all its N2 atoms.     

Crystal structure and magnetic measurements of [Cr(en)3] [ZnCl4]Cl

The compound [Cr(en)₃][ZnCl₄]Cl has been synthesized by reaction of CrCl₃·6H₂O, Zn and [Cr(en)₃]₂(SO₄)₃ in HCl. Its molecular and crystalline structure was determined by X-ray diffraction methods, being monoclinic, P2₁/c, a=21.215(3), b=12.532(2), c=13.707(2) Å, β=95.21°, V= 3629(2) ų, D_x=1.738g cm⁻³, MW=474.9, Z= 8, F(000)=1928, λ(Mo Kα)=0.71069 Å, μ(Mo Kα)= 27.04 cm⁻¹, 288 K. No significant exchange interactions between Cr(III) cations in the crystalline lattice were found. Curie-Weiss behavior was found in the three directions tested (g₁=2.06±0.02,g₂= 2.08±0.02,g₃=2.09±0.01), T=1.2-1.4 K.     

New bis(azolylcarbonyl)pyridine chromium(III) complexes as initiators for ethylene polymerization

Reaction of 2,6-pyridinedicarbonyl dichloride with 3,5-dimethylpyrazole and 1H-indazole, respectively, yield the tridentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylcarbonyl)pyridine (1) and 2,6-bis(indazol-1-ylcarbonyl)pyridine (2). The molecular structure of the new compound (2) was determined by single-crystal X-ray diffraction. These ligands react with CrCl₃(THF)₃ in THF to form neutral complexes of general formula [CrCl₃{2,6-bis(azolylcarbonyl)pyridine-N,N,N}] (3, 4) which were isolated in high yield as air stable green solids and characterized by elemental analysis, magnetic moment, IR, and mass spectroscopies. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active for the polymerization of ethylene.     

Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL)] (HL = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL¹), 3,5-bis(2-pyridyl)pyrazole (HL²), 3-methyl-5-(2-pyridyl)pyrazole (HL³) and 3-methyl-5-phenylpyrazole (HL⁴) with [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) or [PdCl₂(cod)] gives complexes with stoichiometry [PdCl₂(HL)₂] (HL = HL¹, HL², HL³), [Pt(L)₂] (L = L¹, L², L³) and [MCl₂(HL⁴)₂] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and ¹H NMR spectroscopies. The crystal and molecular structure of [PdCl₂(HL¹)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl₂(HL¹)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL¹ is not completely planar.     

Single molecule magnet: Heterodinuclear cyano-bridged cubic cluster [(Tp)8Fe4Ni4(CN)12] (Tp = hydrotris(1-pyrazolyl)borate)

The octanuclear cyano-bridged cluster [(Tp)₈Fe₄Ni₄(CN)₁₂] · H₂O · 24CH₃CN (1) (Tp = hydrotris(1-pyrazolyl)borate) showing magnetic properties of single-molecule magnet has been synthesized by reaction of [fac-Fe(Tp)(CN)₃]⁻ with {(Tp)Ni(NO₃)} species formed from an equimolar reaction mixture of Ni(NO₃)₂ · 6H₂O and KTp in MeCN. The X-ray analysis of 1 shows molecular cube structure in which Fe^III and Ni^II ions reside in alternate corners. The average intramolecular Fe?Ni distance is 5.124 Å. Out-of-phase ac susceptibility and reduce magnetization measurements show that 1 is a single molecule magnet with ground spin state S = 6 and spin reversal energy barrier U = 14 K. Magnetic hysteresis loops were also observed by applying fast sweeping field.     

Copper(II) nitrato and chloro complexes with sterically hindered tridentate ligands: Influence of ligand framework and charge on their structure and physicochemical properties

Copper(II) coordination complexes of the neutral ligand, tris(3-tert-butyl-5-methyl-1-pyrazolyl)methane (L2′), i.e. the copper(II) nitrato complexes [Cu(L2′)(NO₃)][Cu(NO₃)₄]_1/2 (1) and [Cu(L2′)(NO₃)](ClO₄) (2) and the copper(II) chloro complex [Cu(L2′)(Cl)](ClO₄) (3), and its anionic borate analogue, hydrotris(3-tert-butyl-5-methyl-1-pyrazolyl)borate (L2⁻), i.e. the copper(II) nitrato complex [Cu(L2)(NO₃)] (4) and the copper(II) chloro complex [Cu(L2)(Cl)] (5), were synthesized in order to investigate the influence of ligand framework and charge on their structure and physicochemical properties. While X-ray crystallography did not show any definitive trends in terms of copper(II) atom geometry in four-coordinate copper(II) chloro complexes 3 and 5, different structural trends were observed in five-coordinate copper(II) nitrato complexes 1, 2, and 4. These complexes were also characterized by spectroscopic techniques, namely, UV-Vis, ESR, IR/far-IR, and X-ray absorption spectroscopy.     

Syntheses, properties, and structural characteristics of several new [tetrakis(1-pyrazolyl)borato]samarium(III) complexes: comparative study of the B(pyrazolyl)4 and BH(pyrazolyl)3 ligation

Although reactions of samarium(III) chloride, SmCl₃ · 6H₂O, with potassium hydrotris(1-pyrazolyl)borate K[BH(pz)₃] (pz = 1-pyrazolyl) in a molar ratio of (1/1) in THF afford [SmCl{BH(pz)₃}₂(Hpz)], similar reactions with K[B(pz)₄] gave rise to separation of anhydrous H[B(pz)₄]. The homoleptic eight-coordinate complex [Sm{B(pz)₄}₃] obtained from SmCl₃ · 6H₂O and threefold moles of K[B(pz)₄] was allowed to react with twofold moles of K[BH(pz)₃] to give a mixture of three major species [Sm{B(pz)₄}_n{BH(pz)₃}_(3 − n)] (n = 2, 1, 0), whereas similar reactions of [Sm{BH(pz)₃}₃] with K[B(pz)₄] did not proceed at all. The acetylacetonato (acac) complex [Sm{B(pz)₄}₂(acac)], derived from the triflate “Sm{B(pz)₄}₂(OTf)”, was treated with twofold moles of K[BH(pz)₃] and showed its quantitative conversion to [Sm{BH(pz)₃}₂(acac)]. However, analogous reaction of [Sm{BH(pz)₃}₂(acac)] with K[B(pz)₄] did not proceed. Accordingly, samarium(III) ion was determined to prefer coordination of BH(pz)₃ ligand to that of B(pz)₄, indicating less σ-donating electronic character of the latter. The complexes [Sm{B(pz)₄}₂(L-L)] (L-L = β-ketoenolato) in toluene-d₈ exhibited ¹H NMR spectroscopic equivalence of all four pyrazolyl groups at high temperatures, and are regarded as a new class of B(pz)₄ complexes, showing fast intramolecular exchange of their coordinated and uncoordinated pyrazolyl groups. Four compounds were crystallographically characterized.     

Substitution reactions of tetrahydrofuran in [Cr(thf)3Cl3] with mono and bidentate N-donor ligands: X-ray crystal structures of [Cr(bipy)(OH2)Cl3] and [HpyNH2][Cr(bipy)Cl4]

Substitution of thf ligands in [Cr(thf)₃Cl₃] and [Cr(thf)₂(OH₂)Cl₃] was investigated. 2,2′-Bipyridine (bipy) was reacted with [Cr(thf)₃Cl₃] to form [Cr(bipy)(thf)Cl₃] (1), which was subsequently reacted with water to give [Cr(bipy)(OH₂)Cl₃] (2). Reaction of 1 with acetonitrile (CH₃CN), pyridine (py) and pyridine derivatives to form [Cr(bipy)(L)Cl₃] (L = CH₃CN 3, py 4 and 4-pyR with R = NH₂5, Bu^t6 and Ph 7). In addition, the substitution of bipy in [Cr(thf)₃Cl₃] was followed by ¹H NMR spectroscopy at room temperature, which showed completion of the reaction in ca. 100 min. Complex 2 was characterised by single crystal X-ray diffraction. The theoretical powder diffraction pattern of 2 was compared to the experimentally obtained powder X-ray diffraction pattern, and shows excellent agreement. The dimer [Cr₂(bipy)₂Cl₄(μ-Cl)₂] was cleaved asymmetrically to give the anionic complex [Cr(bipy)Cl₄]⁻ (8) and [Cr(bipy)₂Cl₂]⁺ (9). Complexes 8 and 9 were characterised by single crystal X-ray diffraction.     

Decomposition of reactive oxygen species by copper(II) bis(1-pyrazolyl)methane complexes

Two bis(1-pyrazolyl)alkane ligands, bis(3,5-dimethyl-1-pyrazolyl)methane and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methane, and their copper(II) complexes, bis(3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL₁(NO₃)₂] and bis(4-iodo-3,5-dimethyl-1-pyrazolyl)methanedinitratocopper(II) [CuL₂(NO₃)₂]·2H₂O, were prepared. Physiochemical properties of the copper(II) complexes were studied by spectroscopic (UV–vis, IR, EPR) techniques and cyclic voltammetry. Spectroscopic analysis revealed a 1:1 stoichiometry of ligand:copper(II) ion and a bindentate coordination mode for the nitrate ions in both of the complexes. According to experimental and theoretical ab initio data, the copper(II) ion is located in an octahedral hexacoordinated environment. Both complexes were able to catalyze the dismutation of superoxide anion () (pH 7.5) and decomposition of H₂O₂ (pH 7.5) and peroxynitrite (pH 10.9). In addition, both complexes exhibited superoxide dismutase (SOD) like activity toward extracellular and intracellular reactive oxygen species produced by activated human neutrophils in whole blood. Thus, these complexes represent useful SOD mimetics with a broad range of antioxidant activity toward a variety of reactive oxidants.     

Hydrogen bond supramolecular self-assembly in nickel(II) dithiophosphates, Ni[S2P(OR)2]2, R = sec-Bu, iso-Bu, and their bis(pyrazole) adducts

The reaction between nickel(II) nitrate and potassium phosphorus-1,1-dithiolates (di-sec-butyl and di-iso-butyl) in methanol yields 2:1 complexes which were characterized by FT-IR and NMR spectroscopy. 2:1 pyrazole adducts of both compounds were also obtained.The X-ray diffraction analysis of the compounds reveals square planar, four-coordination geometry for the homoleptic compounds and a six-coordinated distorted octahedral geometry for the adducts. In Ni[S₂P(OBu^s)₂]₂ the molecules are associated through C-H?O hydrogen bonds (2.652 Å), and in Ni[S₂P(OBuⁱ)₂]₂ the molecules are associated through C-H?S hydrogen bonds (2.948 Å). The pyrazole adducts are associated through N-H?O bonds and N-H?S bonds from the pyrazole nitrogen atoms, to form supramolecular assemblies. Thus, Ni[S₂P(OBu^s)₂(Pz)₂]₂ (Pz = pyrazole) forms bi-dimensional layers through N-H?O and N-H?S bonds (2.502 and 2.965 Å, respectively), whereas Ni[S₂P(OBuⁱ)₂(Pz)₂]₂ forms linear chains with N-H?S bonds 2.728 Å. The dithiophosphato groups behave as isobidentate chelating ligands.     

Magnesium hydrotris(1-pyrazolyl)borate as a promising single source MOCVD precursor of magnesium borate phases

The magnesium(II) hydrotris(1-pyrazolyl)borate, Mg[BH(pz)₃]₂, complex has been, for the first time, tested as a precursor for the metal organic chemical vapor deposition (MOCVD) of borate phase thin films. The thermal analyses of this source reveal high volatility and good thermal stability with a low residue left despite its relatively high melting point. In particular, the compound has been successfully applied to the MOCVD fabrication of Mg₂B₂O₅ films, and therefore it represents a suited and reliable single source precursor of borate phases. Mg[BH(pz)₃]₂ provides constant evaporation rates even for very long deposition times and, hence, highly homogeneous films of carefully controlled thickness.     

Silver (I) poly(1,2,4-triazolyl)borate complexes containing monodentate phosphane ligands

New silver (I) derivatives containing monodentate tertiary phosphanes and anionic poly(triazol-1-yl)borate ligands have been prepared from the reaction of AgNO₃ and PR₃ (R = Ph, Bn, o-tolyl, m-tolyl, p-tolyl) and potassium dihydrobis(1,2,4-triazolyl)borate, K[H₂B(tz)₂], or potassium hydrotris(1,2,4-triazolyl)borate, K[HB(tz)₃]; their solid state and solution properties have been investigated through analytical and spectroscopic measurements (IR, ¹H-, and ³¹P NMR). The ¹H- and ³¹P NMR solution spectra in some cases can be interpreted on the basis of a dissociation of [{H₂B(tz)₂}Ag(PR₃)₂] into [{H₂B(tz)₂}Ag(PR₃)] and PR₃. All the compounds are soluble in chlorinated solvents and are non-electrolytes in CH₂Cl₂ and acetone solutions. [{H₂B(tz)₂}Ag(PPh₃)₂] and [{H₂B(tz)₂}Ag{P(m-tolyl)₃}₂] are simple mononuclear arrays, the silver atoms lying in four-coordinate N₂AgP₂ environments. Owing to the presence of the methyl substituents on the phosphane ligand, the complex [{HB(tz)₃}Ag{P(o-tolyl)₃}], as expected, is mononuclear. In [{H₂B(tz)₂}Ag{P(p-tolyl)₃}], the silver environment is still four-coordinate but PAgN₃, utilizing the coordinating capability of one of the additional (‘exo’-) ring nitrogens not only to complete the four-coordinate array about the silver but, necessarily, to link successive asymmetric units into a single-stranded polymer.     

[S2], [S3], and [N3] coordination modes of hydrotris(thioxotriazolyl)borato. Zinc, nickel, cobalt, and bismuth complexes

The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (Tr^Ph,Me) was synthetized as natrium salt and the complexes [Zn(Tr^Ph,Me)₂] · 7.5H₂O · 1.5CH₃CN (2a), [Zn(Tr^Ph,Me)₂] · 8DMF (2b), [Co(Tr^Ph,Me)₂] · 8DMF (3a), [Ni(Tr^Ph,Me)₂] · H₂O · 6DMSO (4a), [Bi(Tr^Ph,Me)₂]NO₃ (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η² and [S₂] for 2a and η³ and [N₃] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η³ and [N₃] coordinated whereas in the bismuth complex the η³ and [S₃] coordination is exhibited.     

Synthesis and structure of chloro(ligand)bis(diphenylglyoximato)cobalt(III) complexes

The synthesis and characterization of trans-chloro- (ligand)bis(diphenylglyoximato)cobalt(III) complexes [ligand = pyridine (py), α-, β-, or γ-picoline (α-pic, β-pic, γ-pic), 3,5-lutidine (lut), p-toluidine (p-tol) and PPh₃] is presented. X-ray crystal structure determination of the pyridine (1) and p-toluidine (6) derivatives has been carried out. Compound 1 crystallizes in the monoclinic system, space group P2₁/n, with Z = 4 and unit cell parameters a = 23.124(4), b = 13.009(3) and c = 11.204(3) Å, and β= 93.14(2)°. Compound 6 crystallizes in the monoclinic system, space group P2₁/n, with Z = 4 and unit cell parameters a = 18.792(3), b = 12.540(2) and c = 15.346(3) Å, and β = 97.54(2)°.     

Conformational flexibility of 2,6-bis(pyrazol-1-ylmethyl)pyridine (L) in [(L)Co(H2O)3]Cl2 and [(L)Ni(H2O)2Cl]Cl·H2O. Molecular structures and non-covalent interactions

Using a non-planar tridentate ligand 2,6-bis(pyrazol-1-ylmethyl)pyridine (L⁵) two new coordination complexes [(L⁵)Co^II(H₂O)₃]Cl₂ (1) and [(L⁵)Ni^II(H₂O)₂Cl]Cl·H₂O (2) have been synthesized and structurally characterized. Complex 1 has N₃O₃ distorted octahedral environment around Co^II with coordination by L⁵ (two pyrazole and a pyridine nitrogen in a facial mode) and three water molecules. Complex 2 has N₃O₂Cl distorted octahedral geometry around Ni^II with meridional L⁵ coordination, two water molecules, and a Cl⁻ ion. Analysis of the crystal packing diagram reveals the involvement of solvent (water as metal-coordinated and as solvent of crystallization) and counteranion (Cl⁻) to play significant roles in generating 1D chains, involving O-H···Cl, and O-H···O interactions.     

Cation effect on energy transfer reactions from [Tb(2,6-pyridinedicarboxylate)3] to anionic chromium(III) and neodymium(III) complexes in aqueous solutions

Cation effects are studied on the excitation energy transfer reaction between anionic complexes, i.e., [Tb(dpa)₃]³⁻ (dpa=2,6-pyridinedicarboxylate) quenched by [Cr(ox)₃]³⁻ (ox=oxalate ion), [Cr(mal)₃]³⁻ (mal=malonate ion) and [Nd(dpa)₃]³⁻ in aqueous solutions in the presence of alkali metal ions added for adjustments of ionic strengths. In the quenching reaction of [Cr(ox)₃]³⁻, magnitudes of quenching rate constants (k_q) and energy transfer rate constant in encounter complex (k₁) are changed by the cations in the order of Li⁺ < Na⁺ < K⁺ ≈ Rb⁺ ≈ Cs⁺, that is quite contrary of the cation effect on energy transfer reaction between [Ru(N-N)₃]²⁺ and [Cr(ox)₃]³⁻, reported in the previous paper. On the other hand, the rate constants in quenching reactions by [Cr(mal)₃]³⁻ and [Nd(dpa)₃]³⁻ remain almost constant. This result indicates that more separated donor-acceptor pair is not sensitive to coexisting cations.