Synthesis, characterization and chromotropic properties of MnII, CoII, NiII and CuII with bis (acesulfamato) bis ( 3 -methylpyridine) complexes

The novel 3- [M: Mn^II, Co^II, and Ni^II] and 3- complexes (acs: acesulfamate; 3-pic: 3-methylpyridine) have been synthesized and characterized using elemental analyses, magnetic moments, UV–Vis and FT-IR spectra. The thermal behaviour of the complexes was also studied by simultaneous TG, DTG and DTA methods in static air atmosphere. The chromotropic properties of all complexes have been studied using thermal and spectral analysis. While the complexes of Co^II and Ni^II show reversible continuous thermochromism, an irreversible discontinuous thermochromism is observed in the Mn^II and Cu^II) complexes in the solid state. The observed thermochromism in the Mn^II, Co^II and Ni^II complexes is due to the different ligand field strength associated with the deaquation reaction. The solvatochromic behaviour of the complexes is also studied and all anhydrous complexes (except Mn^II) exhibit solvatochromic properties depending on the donor number of the solvent.     

Binary Cyclo-Tetraphosphates as New Special Pigments

Abstract

The binary cyclo-tetraphosphates Me_2-xIIP₄O₁₂ as new inorganic compounds (M^II=Zn, Mn,Co; M^II=Ca,Mg) have been prepared in our laboratory. The products were tested as special pigments (for anti-corrosion, ceramic, luminescence purposes and as pearlescent pigments).     

Oximato bridged RhIII2MII and RhIIIMI species (MII = Mn, Co, Ni; MI = Cu, Ag)

The reaction of [RhCl₂(HPhL)(PhL)] with M^II(ClO₄)₂·6H₂O in presence of alkali has furnished trinuclear [RhCl₂(PhL)₂]₂M(H₂O)₂·H₂O (HPhL is phenylazobenzaldoxime; M = Mn, Co, Ni). A similar reaction with M^I(PPh₃)₂NO₃ yielded binuclear [RhCl₂(PhL)₂]M(PPh₃)₂ (M = Cu, Ag). In these molecules the oximato group acts as a bridge between Rh^III (bonded at N) and M^II or M^I (bonded at O). In structurally characterized [Rh^IIICl₂(PhL)₂]₂Mn(H₂O)₂.H₂O the centrosymmetric distorted octahedral MnO₆ coordination sphere is spanned by four oximato oxygen atoms and two water molecules lying in trans position. In the lattice the neighbouring molecules are held together by H₂O⋯H₂O⋯H₂O hydrogen bonds generating infinite zigzag chains. The manganese atoms lie parallel to the C-axis, the shortest Mn...Mn distance being 7.992 ?. Magnetic exchange interactions if any are small as seen in room temperature magnetic moments. The manganese system displays a strong EPR signal near g = 2.00. In the complex [RhCl₂(PhL)₂]Cu(PPh₃)₂ the copper atom is coordinated to two oximato oxygen atoms and the two phosphorus atoms in a distorted tetrahedral geometry. The softness of the phosphine ligand is believed to sustain the stable coordination of hard oximato oxygen to soft Cu^I. The coordination sphere of the RhIII atom in both the complexes is uniformly trans-RhN₄Cl₂.     

Contrasting picosecond photokinetics of CoII and CoIII porphyrins verify excited-state predictions

Using picosecond transient absorption techniques, we have different low-lying excited states for several Co^II and Co^III porphyrins. These differences are interpreted in terms of theoretical calculations that predict the lowest-energy excited states to be ²(π·d) in Co^II and ³(d, d) in Co^III.     

The unprecedented role of a CuII cryptand in the luminescence properties of a EuIII cryptate complex

Abstract  

A Eu^III cryptate complex constructed from a Cu^II cryptand with an L ^tBu ligand, [Eu^IIICu₂^II(L ^tBu)₂(NO₃)₃(MeOH)], and the corresponding Ca^II and Na^I cryptates, [Ca^IICu₂^II(L ^tBu)₂(NO₃)₂(MeOH)₂] and [Na^ICu₂^II(L ^tBu)₂(Me₂CO)](BPh₄), have been synthesized and characterized in order to shed light on the essential role of Cu^II in the luminescence of a Eu^III cryptate. The unprecedented role of a Cu^II cryptand makes it possible to produce lanthanide luminescence in a Eu^III cryptate complex and is successfully elucidated by comparison with the corresponding Ca^II and Na^I cryptates.     

Water‐Exchange Mechanism for Zinc(II), Cadmium(II), and Mercury(II) Ions in Water as Studied by Umbrella‐Sampling Molecular‐Dynamics Simulations

Umbrella‐sampling molecular‐dynamics simulations were performed to investigate the water‐exchange reactions of zinc(II), cadmium(II), and mercury(II) ions in aqueous solution. The dissociation of a coordinating water molecule to the M? O distance at 3.34, 3.16, and 3.26 Å for Zn^II, Cd^II, and Hg^II, respectively, leads the system to a transition state. For Zn^II, the first hydration shell is occupied by five spectator water molecules in the transition state, indicating that the water‐exchange reaction proceeds via a dissociative mode of activation. In contrast, the number of spectator water molecules of 5.85 and 5.95 for Cd^II and Hg^II, respectively, suggests an associative exchange for these larger metal ions. The average M? O distance of the spectator molecules is shortened by 0.06 Å for the dissociative exchange of Zn^II, while it is elongated by 0.04 and 0.03 Å for Cd^II and Hg^II, respectively. The water‐exchange rate constants of 4.1×10⁸, 6.8×10⁸, and 1.8×10⁹ s^?1 are estimated for Zn^II, Cd^II, and Hg^II, respectively, at 298 K in terms of the transition‐state theory based on the assumption of a transmission coefficient of unity.     

Synthesis and spectral characterization of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,4- bis (2-carboxyaldehydephenoxy)butane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:15,16-tribenzo-9,15-dioxacycloheptadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine with 1,4-bis(2-carboxyaldehydephenoxy)butane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,4-bis (2-carboxyaldehydephenoxy)butane and Cu(NO₃)₂ · 3H₂O, Ni(NO₃)₂ · 6H₂O, Pb(NO₃)₂, Co(NO₃)₂ · 6H₂O, La (NO₃)₃ · 6H₂O, respectively. The ligand and its metal complexes were characterized by elemental analysis, IR, ¹H- and ¹³C-n.m.r., UV-vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements and mass spectra. All complexes are diamagnetic and the Cu^II complex is binuclear. The Co^II complex was oxidised to Co^III.     

High-Temperature Synthesis of the Mg2-x Ca xP4O12 and Cd2-x CaxP4O12

Abstract

The cyclo-tetraphosphates of the M^II _2-xCa_xP₄O₁₂ type (MI^II = Mg, Cd) have been synthetized as new binary compounds, and their existence for x ε (0; 1 > (Mg) or for x ε (0; 0.7 > (Cd) has been proved. The synthesis is based on a two-step thermal process. The first step starts from pure cyclo-tetraphosphates of the two divalent metals and Ca(PO₃)₂ which are melted in normal atmosphere and then abruptly cooled to give a vitreous amorphous product composed of higher linear phosphates of the summary formula (M^II _2-x Ca_x)_n/4H₂P_nO_3n+1 · In the second step, this product is repeatedly heated to a suitable temperature and recrystallized to give microcrystalline product M^II _2-x Ca_xP₄O₁₂ · The colourless (white) products crystallize in the monoclinic aystem, C2c group. Their structural parameters have the values for Mg_2-x Ca_xP₄O₁₂: a = 11.749(5) to 12.063(4) Å, b = 8.278(4) to 8.635(4) Å c = 9.905(4) to 9.875(3) Å and β = 118.92(2)° to 118.03(2)°; or for Cd_2-x Ca_xP₄O₁₂: a = 12.328(4) to 12.457(5) Å b = 8.639(3) to 8.732(4) Å c = 10.388(3) to 10.443(4) Å and β = 119.33(2)° to 119.45(2)°.     

Macrocyclic effects upon isomeric CuIIMII and MIICuII cores. Formation with unsymmetric phenol-based macrocyclic ligands

This paper discusses coordination-position isomeric M^IICu^II and Cu^IIM^II complexes, using unsymmetric dinucleating macrocycles (L^m;n)²⁻ ((L^2;2)²⁻, (L^2;3)²⁻ and (L^2;4)²⁻) that comprise two 2-(N-methyl)-aminomethyl-6-iminomethyl-4-bromo-phenonate entities, combined through the ethylene chain (m = 2) between the two amine nitrogens and through the ethylene, trimethylene or tetramethylene chain(n = 2, 3 or 4) between the two imine nitrogens. The macrocycles have dissimilar N(amine)₂O₂ and N(imine)₂O₂ metal-binding sites sharing the phenolic oxygens. The reaction of the mononuclear Cu^II precursors, [Cu(L^2;2)], [Cu(L^2;2)] and [Cu(L^2;2)], with a M^II perchlorate and a M^II acetate salt formed (acetato)M^IICu^II complexes: [CoCu(L^2;2)(AcO)]ClO⁴·0.5H₂O] (1), [NiCu(L^2;2) (AcO)]ClO₄ (2), [ZnCu(L^2;2) (AcO)]ClO₄ (3), [CoCu(L^2;3)(AcO)]ClO₄·0.5H₂O (4), [NiCu(L^2;3)(AcO)]ClO₄ (5), [ZnCu(L^2;3)(AcO)]ClO₄·0.5H₂O (6), [CoCu(L^2;4)(AcO)(DMF)]ClO₄ (7), [NiCu(L^2;4) (AcO)]ClO₄·2DMF (8) and [ZnCu(L^2;4)(AcO)]ClO₄ (9) (the formulation [M_aM_b (L^m;n)]²⁺ means that M_a resides in the aminic site and M_b in the iminic site). The site selectivity of the metal ions is demonstrated by X-ray crystallographic studies for 2·MeOH,3,5,7, and9. An (acetato)Cu^IIZn^II complex, [CuZn(L^2;3)(AcO)]ClO₄ (10), was obtained by the reaction of [PbCu(L^2;3)]-(ClO₄)₂ with ZnSO₄·4H₂O, in the presence of sodium acetate. Other complexes of the Cu^IIM^II type were thermodynamically unstable to cause a scrambling of metal ions. The Cu migration from the iminic site to the aminic site in the synthesis of10 is explained by the ‘kinetic macrocyclic effect’. The coordination-position isomers,6 and10, are differentiated by physicochemical properties.     

Peculiarities of the thermal polymerization of the complex-bonded acrylamide

Peculiarities of the thermal polymerization of acrylamide bonded in a complex with Co^II, Ni^II, or Cu^II nitrate have been studied by differential scanning calorimetry. The polymerization can occur in the regions prior to the melting of the complex, during melting, or right after it, depending on the rate of heating and the nature of the complexing agent. The effect of the addition of water and inorganic or polymeric powders on the form and character of the polymerization thermograms, which have a complex multimodal structure in the polymerization region, has been studied. The analysis of the results obtained indicates that during heating and melting complexes of a number of structures differing in their polymerization properties are formed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1410–1413, August, 1993.     

Study of the structure of molecular complexes. Coordination numbers for Li+, Na+, K+, F− and Cl− in water

A cluster of 200 water molecules containing a single ion (either Li⁺ or Na⁺ or K⁺ or F^? or Cl^?) has been studied at T = 298 K using Monte Carlo techniques. The waterwater interaction is obtained from a quantum-mechanical study of CI type; the ionwater potentials have been obtained from HartreeFock type computations. The computed coordination numbers in the first shell for Li⁺, Na⁺, K⁺, F^? and Cl^? are 4.0, 4.3, 5.1, 3.85 and 4.3, respectively; the corresponding first hydration shell radii are 2.28 Å, 2.59 Å, 3.27 Å, 1.99 Å and 2.85 Å, respectively. A discussion of the second and third hydration shell radii and coordination numbers is given.     

Synthesis and electrochemical characterization of CoII, NiII, and CuII complexes with organic N2S2-type ligands derived from 2-thio-substituted benzaldehydes and aromatic amines

Transition metal complexes (Ni^II, Co^II, and Cu^II) with tetradentate N₂S₂-type ligands (L), which are reaction products of 2-thio-substituted benzaldehydes with aromatic amines (3-aminopyridine or 2-aminothiophenol), were synthesized for the first time. The complexes have the composition L·MX₂ or L·2MX₂ (X = Cl or ClO₄). The electrochemical behavior of the ligands and complexes was studied by cyclic voltammetry and rotating disk electrode voltammetry. Depending on the structure of the complexes, the metal atom in the latter is initially reduced in a one-or two-electron process. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2124, November, 2007.     

Synthesis, characterization and redox properties of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,3- bis (2-carboxyaldehyde phenoxy)propane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:,14,15-tribenzo-9,13-dioxacyclohexadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,3-bis(2-carboxyaldehyde phenoxy)propane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by a template effect by reaction of 2,6-diaminopyridine and 1,3-bis (2-carboxyaldehyde phenoxy)propane and Cu O, Ni O, Co O, La O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H- and ¹³C-NMR-, UV-vis spectra, magnetic susceptibility, conductivity measurements, mass spectra and cyclic voltammetry. All complexes are diamagnetic and the Cu^II complex is binuclear. The diamagnetic behaviour of the binuclear complex may be explained by a very strong anti-ferromagnetic interaction in the Cu–Cu pair. The Co^II was oxidised to Co^III.     

Reversible and Stepwise Single-Crystal-to-Single-Crystal Transformation of a Platinum(II) Complex with Vapochromic Luminescence

The vapochromic single-crystal-to-single-crystal (SCSC) transformation of a highly luminescent Pt^II complex bearing an N-heterocyclic carbene [Pt(CN)₂(tBu-impy)] (tBu-impyH⁺=1-tert-butyl-3-(2-pyridyl)-1H-imidazolium) is reported. The trihydrate form of the complex, which exhibits blue ³MMLCT emission owing to weak Pt⋅⋅⋅Pt interactions, changed its luminescence color from blue to yellowish-green upon the desorption of water molecules while keeping the high emission quantum yield of more than 0.45. Variable-temperature and continuous in-situ tracking of single-crystal X-ray diffraction measurements revealed that the SCSC transformation proceeds reversibly by the release and reabsorption of water molecules, thereby changing the stacked structure slightly. As a result, the dynamics of vapor-induced SCSC transformation were elucidated: that the anhydrous form returned to the original trihydrate form in a two-step process under a water vapor atmosphere. In addition, the Pt^II complex exhibited a similar SCSC response accompanied by a luminescence color change in the presence of methanol vapor, while being inactive toward ethanol vapor.     

Cyclohexylethynyl complexes of CoII and FeII

This paper deals with the synthesis of six σ-cyclohexylethynyl complexes of Co^II and Fe^II and their characterization by chemical analysis, infrared and ¹H NMR spectra, and magnetic measurements. Four of them are six-coordinate complexes, unsubstituted or substituted, namely K₄[M(C≡C—C₆H₁₁)₆] nNH₃(M = Co, n = 2; M = Fe, n = 0), K₂[Co(C≡C₆H₁₁)₄(NH₃)₂] and K₄[Fe(CN)₄-(C≡C—C₆H₁₁)₂]. Two are four-coordinate complexes of formula [(Ph₃P)₂M-(C≡C₆H₁₁)₂] (M = Co, Fe). All are low-spin complexes, the magnetic moment for the six-coordinate Co(II) complexes, measured at various temperatures, being intermediate between low- and high-spin values.     

Poly[[tetraaqua(μ7‐pyridine‐2,3,5,6‐tetracarboxylato)dicadmium(II)] monohydrate]

The title compound, {[Cd₂(C₉HNO₈)(H₂O)₄]·H₂O}_n, consists of two crystallographically independent Cd^II cations, one tetrabasic pyridine‐2,3,5,6‐tetracarboxylate (pdtc) anion, four coordinated water molecules and one solvent water molecule. The Cd^II cations have distorted square‐antiprismatic (one pyridine N, six carboxylate O and one water O atom) and octahedral (three carboxylate O and three water O atoms) coordination environments. Each pdtc ligand employs its pyridine and carboxylate groups to chelate and bridge seven Cd^II cations. The square‐antiprismatic coordinated Cd^II cations are linked by pdtc ligands into a lamellar framework structure, while the octahedral coordinated Cd^II cations are bridged by the μ₂‐carboxylate O atoms and the pdtc ligands into a chain network that further joins neighbouring lamellae into a three‐dimensional porous network. The cavities are filled with solvent water molecules that are linked to the host through complex hydrogen bonding.     

A EuII‐Containing Cryptate as a Redox Sensor in Magnetic Resonance Imaging of Living Tissue

The Eu^II ion rivals Gd^III in its ability to enhance contrast in magnetic resonance imaging. However, all reported Eu^II‐based complexes have been studied in vitro largely because the tendency of Eu^II to oxidize to Eu^III has been viewed as a major obstacle to in vivo imaging. Herein, we present solid‐ and solution‐phase characterization of a Eu^II‐containing cryptate and the first in vivo use of Eu^II to provide contrast enhancement. The results indicate that between one and two water molecules are coordinated to the Eu^II core upon dissolution. We also demonstrate that Eu^II‐based contrast enhancement can be observed for hours in a mouse.     

Investigation on the thermal decomposition some heterodinuclear NiII-MII complexes prepared from ONNO type reduced Schiff base compounds ( M II=ZnII, CdII)

N,N′-bis(salicylidene)-1,3-propanediamine (LH₂), N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂), N,N′-bis(salicylidene)-2-hydroxy-1,3-propanediamine (LOH₃), N,N′-bis(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH₂) and N,N′-bis(2-hydroxyacetophenone)-2,2′-dimethyl-1,3-propanediamine (LACDMH₂) were synthesized and reduced to their phenol-amine form in alcoholic media using NaBH₄ (L^HH₂, LDM^HH₂, LOH^HH₂, LAC^HH₂ and LACDM^HH₂). Heterodinuclear complexes were synthesized using Ni(II), Zn(II) and Cd(II) salts, according to the template method in DMF media. The complex structures were analyzed using elemental analysis, IR spectroscopy, and thermogravimetry. Suitable crystals of only one complex were obtained and its structure determined using X-ray diffraction, NiLAC^H·CdBr₂·DMF₂, space group orthorhombic, Pbca, a=20.249, b=14.881, c=20.565 ? and Z=8. The heterodinuclear complexes were seen to be of [Ni·ligand·MX₂·DMF₂] structure (ligand=L^H2−, LDM^H2−, LOH^H2−, LAC^H2−, LACDM^H2−, M=Zn^II, Cd^II, X=Br⁻, I⁻). Thermogravimetric analysis showed irreversible bond breakage of the coordinatively bonded DMF molecules followed by decomposition at this temperature.     

Coordination de la phosphine organo-fer [CpFeIIC6Me5CH2PPh2]+ au RhI et proprietes spectroscopiques,electrochimiques et catalytiques des complexes heterobinucleaires FeII-RhI

The reactions between the phosphine-organoiron [CpFe^II-η⁶-C₆Me₅CH₂PPh₂]⁺ PF₆^? (1) and [RhCl(η⁴-diolefin)(μ-Cl)]₂ in CH₂Cl₂ at reflux give the new heterobinuclear air-stable crystalline complexes [CpFe^II-η⁶-C₆Me₅CH₂)P(Ph)₂Rh(η⁴-diene)Cl]PF₆,(D'*-diene=cyclooctadiene (COD): 65%, 2; trimethylfluorobenzobicyclo[2.2.2]octadiene (Me₃TFB): 48%, 3). Complexes 2 and 3 have been studied by ¹H, ¹³C and ³¹P NMR spectroscopy and they are carbonylated (CO, 1 atm). Cyclic voltammetry experiments with addition of MeOH show electron transfer Fe^IRh^I → Fe^IIRh⁰, the presence of a catalytic wave Fe^I/Fe^II and the possible formation of Rh hydrides. Under normal conditions 2 is a catalyst for hydrogenation of cyclohexene, but it is less efficient than the known mononuclear Rh¹ analogues.     

Reaction of (±)-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-phosH} with copper(II), cobalt(II) and iron(II) compounds; Identification by x-ray diffraction of [Co(CH3OH)4(H2O)2][(+)-phos][(−)-phos]. 2CH3OH·H2O

[Cu₂(μO₂CCH₃)₄(H₂O)₂], [CuCO₃·Cu(OH)₂], [CoSO₄·7H₂O], [Co((+)-tartrate)], and [FeSO₄·7H₂O] react with excess racemic (±)- 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-PhosH} to give mononuclear Cu^II, Co^II and Fe^II products. The cobalt product, [Co(CH₃OH)₄(H₂O)₂]((+)-Phos)((−)-Phos) ·2CH₃OH·H₂O (7), has been identified by X-ray diffraction. The high-spin, octahedral Co^II atom is ligated by four equatorial methanol molecules and two axial water molecules. A (+)- and a (−)-Phos⁻ ion are associated with each molecule of the complex but are not coordinated to the metal centre. For the other Co^II, Cu^II and Fe^II samples of similar formulation to (7) it is also thought that the Phos⁻ ions are not bonded directly to the metal. When some of the Cu^II and Co^II samples are heated under high vacuum there is evidence that the Phos⁻ ions are coordinated directly to the metals in the products.