E.s.r. and electrochemical studies of four- and five-coordinate copper(II) complexes containing mixed ligands

Heterocyclic base adducts of salicylaldehyde N(4)- cyclohexylthiosemicarbazone(H2L) copper(II) complexes have been synthesized and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as i.r., electronic and 1H- and 13C-n.m.r. spectra of the thiosemicarbazone have been obtained. Based on e.s.r. studies, all possible parameters have been calculated. The g values, calculated for all the complexes in frozen solution, indicate the presence of the unpaired electron in the dx2−y2 orbital. The metal–ligand bonding parameters evaluated showed strong in-plane σ- and in-plane π-bonding. The magnetic and spectroscopic data indicate a square-planar geometry for the four-coordinate and a distorted square-pyramidal structure for the five-coordinate complexes. From cyclic voltammetric data quasireversible copper(II)/copper(I) couples are observed for the complexes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Structures, electronic properties and solid state luminescence of Cu(I) iodide complexes with 2,9-dimethyl-1,10-phenanthroline and aliphatic aminomethylphosphines or triphenylphosphine

The luminescent complexes of triphenylphosphine and two interesting aminomethylphosphines: P(CH(2)N(CH(2)CH(2))(2)NCH(3))(3) and P(CH(2)N(CH(2)CH(2))(2)O)(3) with copper(I) iodide and 2,9-dimethyl-1,10-phenanthroline (dmp): [CuI(dmp)PPh(3)], [CuI(dmp)P(CH(2)N(CH(2)CH(2))(2)NCH(3))(3)] and [CuI(phen)P(CH(2)N(CH(2)CH(2))(2)O)(3)] are presented in this work. These complexes were characterized in solution by means of NMR spectroscopy and their structures were crystallographically determined in the solid state. All complexes crystallize as the discrete dimers bound by π-stacking interactions between dmp rings. The coordination geometry about the Cu(I) centre is pseudo-tetrahedral showing small flattening and large rocking distortions. The investigated compounds exhibit intense orange photoluminescence in the solid state (emission peaks at r.t.: λ(max) = 588-592 nm; τ = 1.7-2.2 and 6.4-10.0 μs; at 77 K: λ(max) = 605-612 nm; τ = 4.8-6.5 and 32-47 μs), which is several orders higher than the luminescence of the analogous complexes with 1,10-phenanthroline (phen). Electronic and structural properties of the [CuI(dmp/phen)PR(3)] complexes were characterized using DFT methods to interpret their photophysics. On the basis of TDDFT calculations the broad CT bands observed in UV-Vis spectra are interpreted as the two mixed transitions from σ(CuI) bond with a small admixture of σ(CuP) bond to π* phen or dmp ligand: (MX,MPR(3))LCT, while the emissions most probably occur from two triplet states which are in thermal equilibrium.     

Homo and heteronuclear complexes of dioxime ligands

The mononuclear fragments [Cu(HDopn)(OH)2]+ and [Cu(HPopn)(OH)2]+, [H2Dopn=3,3-(trimethylene- dinitrilo)-dibutan-2–one dioximate and H2Popn, = 3, 3-(phenylenedinitrilo)-dibutan-2–one dioximate] were used to prepare four binuclear complexes [(OH2)Cu (Dopn)Cu(ditn)]2+, [(OH2)Cu(Dopn)Ni(ditn)(H2O)]2+ (ditn=diethylenetriamine) and [(OH2)Cu(Popn)Cu(L) (H2O)]2+ (L=2,2-bipyridine or 1,10–phenanthroline). Two trinuclear complexes, [{Cu(Popn)(OH2)}2M (H2O)n]2+ (when M=CuII, n=1; M=ZnII, n= 2), have been synthesised and characterised by elemental analyses, f.a.b. mass, i.r., electronic, e.s.r. spectroscopy and variable temperature (5–300K) magnetic susceptibility measurements. A strong antiferromagnetic interaction (J=–545cm–1 to –700cm–1) has been found for the binuclear copper(II) complexes. The X-band e.s.r. spectra of these complexes at 300K and for trinuclear complexes at 120K indicate square-pyramidal geometry for the copper centres with a (dx2–y2)1 ground state. The binuclear complex of copper(II)–nickel(II) centres with antiferromagnetic interaction (J=–107 cm–1) is described, and moderately strong zero-field splitting within the quartet state leads to Kramers doublet, as indicated by X-band e.s.r. spectra of this complex. The trinuclear copper(II) complex with an antiferromagnetic interaction (J= –350cm–1) is also described. The heterometallic trinuclear copper(II)–zinc(II)–copper(II) system shows a very weak interaction (J–1cm–1).     

Synthesis, electronic and ESR spectral studies on copper(II) nitrate complexes with some acylhydrazines and hydrazones

This paper describes the preparation of [Cu(bh)(2)(H(2)O)(2)](NO(3))(2)], [Cu(ibh)(2)(NO(3))(2)], [Cu(ibh)(2)(H(2)O)(2)](NO(3))(2) and [Cu(iinh)(2)(NO(3))(2)] (bh=benzoyl hydrazine (C(6)H(5)CONHNH(2)); ibh=isonicotinoyl hydrazine (NC(5)H(4)CONHNH(2)); ibh=isopropanone benzoyl hydrazone (C(6)H(5)CONHN=C(CH(3))(2); iinh=isopropanone isonicotinoyl hydrazone (NC(5)H(4)CONHN=C(CH(3))(2)). These copper(II) complexes are characterized by elemental analyses, molar conductances, dehydration studies, ESR, IR and electronic spectral studies. The electronic and ESR spectra indicate that each complex exhibits a six-coordinate tetragonally distorted octahedral geometry in the solid state and in DMSO solution. The ESR spectra of most of the complexes are typically isotropic type at room temperature (300K) in solid state as well as in DMSO solution. However, all the complexes exhibit invariably axial signals at 77K in DMSO solution. The trend g(||)>g( perpendicular)>g(e,) observed in all the complexes suggests the presence of an unpaired electron in the [Formula: see text] orbital of the Cu(II). The bh and inh ligands bond to Cu(II) through the >CO and NH(2) groups whereas, ibh and iinh bond through >CO and >CN groups. The IR spectra of bh and ibh complexes also show HOH stretching and bending modes of coordinated water.     

Models for copper proteins. Copper(I) and (II) complexes of a novel binucleating tetraamino-tetrathioether ligand

The novel binucleating ligand, 6,6 prime-methylene-bis(5 prime-amino-3 prime,4 prime-benzo-2 prime-thiapentyl)-1,11-diamino-2,3:9,10-dibenzo-4,8-dithiaundecane (H4L) was prepared and reacted with copper(II) salts in dry MeOH to yield mixtures of copper(I) and copper(II) complexes with Cl- and ClO-4 counter ions. The amine functions on the ligand release protons to form copper(I) complexes: (Cu2L)X2, where X=Cl−, ClO4-. The complexes were oxidized to (Cu2L)X4 with H2O2 in DMF; Cu(NO3)2 gave a different complex, [Cu2(H4L)(NO3)2](NO3)2, as regards proton releasing ability, coordination and oxidation number. Evidence for the structures of this new tetraamino-tetrathioether ligand and its copper complexes is provided by 1H-, 13C-n.m.r., mass, u.v.–vis., i.r. spectra, elemental analyses, molar conductivities and magnetic moments. This revised version was published online in June 2006 with corrections to the Cover Date.     

Stabilities of mixed ligand complexes of Cu(II) with ligands coordinating through O and N : ESR studies

Mixed ligand complexes of Cu(II) with 8-hydroxy-quinolinate (Hy) as one ligand and acetylacetonate (ac.ac) or salicylaldehydate (Sal) as the second ligand have been prepared in reaction mixtures of Cu(Hy)₂ + Cu(ac.ac)₂ and Cu(Hy)₂ + Cu(Sal)₂ in chloroform. Ligand hyperfine structures and the minimum ESR linewidth associated withm = − 3/2 hyperfine component have been used to detect and identify the mixed ligand complexes. The ligands in these complexes coordinate through O or N. The constantsK associated with the ligand exchange equilibriums are ~ 2 at −20°C and are close to the value expected from the empirical relation obtained in an earlier work from a study of Cu(II) complexes in which S also participates in the coordination.     

Solid state structure and solution behaviour of organoselenium(II) compounds containing 2-{E(CH2CH2)2NCH2}C6H4 groups (E = O, NMe)

Cleavage of the Se-Se bond in [2-{O(CH(2)CH(2))(2)NCH(2)}C(6)H(4)](2)Se(2) (1) and [2-{MeN(CH(2)CH(2))(2)NCH(2)}C(6)H(4)](2)Se(2) (2) by treatment with SO(2)Cl(2), bromine or iodine (1 : 1 molar ratio) yielded [2-{O(CH(2)CH(2))(2)NCH(2)}C(6)H(4)]SeX [X = Cl (3), Br (4), I (5)] and [2-{MeN(CH(2)CH(2))(2)NCH(2)}C(6)H(4)]SeI (6). The compounds were characterized in solution by NMR spectroscopy (1H, 13C, 15N, 77Se, 2D experiments). The solid-state molecular structures of 1-3, 4.HBr, 5 and 6 were established by single crystal X-ray diffraction. In all cases T-shaped coordination geometries, i.e. (C,N)SeSe (1, 2), (C,N)SeX (3, 5, 6; X = halogen) or CSeBr(2) (4.HBr), were found. Supramolecular associations in crystals based on hydrogen contacts are discussed.     

Oxidation of electron deficient olefins using a copper(II) complex based on a bis-benzimidazole diamide ligand

New bis-benzimidazole based diamide ligands N, N′-bis(2-methyl benzimidazolyl)-benzene-1,3-dicarboxamide [GBBA] and N-Octyl-N, N′-bis(2-methyl benzimidazolyl)-benzene- 1,3-dicarboxamide [O-GBBA] have been synthesized and utilized to prepare Cu(II) complexes of general composition [Cu(GBBA)X ₂] · nH₂O and [Cu(O-GBBA)X₂] · n H₂O, where X is an exogenous anionic ligand (X = Cl⁻, NO₃⁻, SCN⁻). The oxidation of electron deficient olefins has been investigated using [Cu(O-GBBA)X₂] · nH₂O as catalyst and TBHP as an alternate source of oxygen. The respective ketonic products have been isolated and characterized by ¹H-NMR. The complex [Cu(GBBA)(NO₃)₂] · 4H₂O has been characterized structurally. It crystallizes in a monoclinic space group C2/c. Low temperature EPR spectra have been obtained for the complexes that shows g_II > g_I > 2.0024, indicating a tetragonal geometry in the solution state. The complexes display a quasi reversible redox wave due to the Cu(II)/Cu(I) reduction process. The E_1/2 values shift anodically as NO₃⁻ < SCN⁻ < Cl⁻.     

Near neighbour ligand hyperfine splittings in the e.p.r. spectra of copper(II) complexes

X-band e.p.r. spectra from mixed ligand complexes Cu(btc)-(Hy), Cu(TPA)(Hy) and Cu(Sal)(TPA), have been derived from the spectra of suitable reaction mixtures in CHCl₃ at 25° C (Sal⁻ = salicyladehydate, TPA⁻ = thiopicolineanilide, Hy⁻ = 8-hydroxyquinolinate and btc⁻ =N-benzoyl-N′N′-diethylcarbamide). A digital data acquisition instrument and a personal computer were used for this purpose. The¹⁴N hyperfine splittings observed in these complexes have shown that the observed increase in spin density on the coordinating atoms of one ligand, at the expense of that on the other, is unlikely to be associated with the covalent bonding involving metal d _x ²− _y ²-orbital. Covalent bonding involving metal 4s-orbital component of the unpaired electron orbital has been suggested to be responsible for the observed changes in electron delocalization. This work was carried out during the visit of Drs Z. R. Baratova and P. M. Solozhenkin to India in 1991.     

Syntheses and structures of nickel(II) and copper(II) complexes with biacetyl bis(benzoylhydrazone): one-dimensional self-assembly via π–π interaction and hydrogen bonding

Reactions of Ni(O₂CCH₃)₂·4H₂O and Cu(O₂CCH₃)₂·H₂O with biacetyl bis(benzoylhydrazone) (H₂babh) in alcoholic media afford mononuclear nickel(II) and copper(II) complexes of general formula [M(babh)]. The complexes have been characterized by microanalysis (C, H, N), magnetic susceptibility, and various spectroscopic measurements. X-ray structures of both complexes have been determined. The metal centre in [Ni(babh)] is in square-planar N₂O₂ environment provided by the tetradentate babh²⁻. On the other hand, [Cu(babh)] crystallizes as distorted square-pyramidal [Cu(babh)(CH₃OH)] from methanol. Here the tetradentate babh²⁻ constitutes the N₂O₂ square-base and the O-coordinating methanol occupies the apical site. In the crystal lattice, the molecules of [Ni(babh)] form a one-dimensional π-stacked structure. The [Cu(babh)(CH₃OH)] molecules also form a one-dimensional structure with alternating long and short Cu···Cu distances via intermolecular O–H···N hydrogen bonding and π–π interaction.     

Bivalent transition metal complexes of o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone: spectroscopic, antibacterial, antifungal activity and thermogravimetric studies

Schiff base complexes of Cu(II), Ni(II) and Zn(II) with the o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H(2)o-HAHNH) containing N and O donor sites have been synthesized. Both ligand and its metal complexes were characterized by different physicochemical methods, elemental analysis, molar conductivity ((1)H NMR, (13)C NMR, IR, UV-visible, ESR, MS spectra) and also thermal analysis (TG and DTG) techniques. The discussion of the outcome data of the prepared complexes indicates that the ligand behave as a bidentate and/or tridentate ligand. The electronic spectra of the complexes as well as their magnetic moments suggest octahedral geometries for all isolated complexes. The room temperature solid state ESR spectrum of the Cu(II) complex shows d(x2-y2) as a ground state, suggesting tetragonally distorted octahedral geometry around Cu(II) centre. The molar conductance measurements proved that the complexes are non-electrolytes. The kinetic thermodynamic parameters such as: E(#), ΔH(#), ΔG(#), ΔS(#) are calculated from the DTG curves, for the [Ni(H(O)-HAHNH)(2)] and [Zn(H(2O)-HAHNH)(OAc)(2)]·H(2)O complexes using the Coats-Redfern equation. Also, the antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The [Cu(Ho-HAHNH)(OAc)(H(2)O)(2)] complex was the most active against all strains, including Aspergillus sp., Stemphylium sp. and Trichoderma sp. Fungi; E. coli and Clostridium sp. Bacteria.     

Tunable N-substitution in zwitterionic benzoquinonemonoimine derivatives: metal coordination, tandemlike synthesis of zwitterionic metal complexes, and supramolecular structures

Full details on a very efficient transamination reaction for the synthesis of zwitterionic N,N-dialkyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium derivatives [C6H2(=NHR)2(=O)2] 5-16 are reported. The molecular structures of zwitterions 5 (R=CH3) in 5.H2O, 13 (R=CH2CH2OMe), 15 (R=CH2CH2NMe2), and of the parent, unsubstituted system [C6H2(=NH2)2(=O)2] 4 in 4.H2O have been established by single-crystal X-ray diffraction. This one-pot preparation can be carried out in water, MeOH, or EtOH and allows access to new zwitterions with N-substituents bearing functionalities such as -OMe (13), -OH (9-12), NR1R2 with R1 = or not equal R2 (14-16) or an alkene (8), leading to a rich coordination chemistry and allowing fine-tuning of the supramolecular arrangements in the solid state. As previously described for 15, which reacted with Zn(acac)2 to afford the octahedral Zn(II) complex [Zn[C6H2(NCH2CH2NMe2)O(O)(NHCH2CH2NMe2)]2] (20), ligands 13 and 16 with coordinating "arms" afforded with Zn(acac)2 the 2:1 adducts [Zn[C6H2(NCH2CH2X)O(=O)(NHCH2CH2NX)]2] 19 (X=OMe) and 21 (X=NHEt), with N2O4 and N4O2 donor sets around the octahedral Zn(II) center, respectively. Furthermore, zwitterions 15 and 16 reacted with ZnCl2 to give the stable, crystallographically characterized Zn(II) zwitterionic complexes [ZnCl2[C6H2(NCH2CH2NR1R2)O(=O)(NHCH2CH2NHR1R2)]] 22 (R1=R2=Me) and 23 (R1=Et, R2=H) by means of an unprecedented, tandemlike synthesis in which 1) the two pendant amino groups of the organic benzoquinonemonoimine zwitterionic precursor favor metal coordination and proton transfer and 2) the saturated linker prevents pi-conjugation between the charges. The nature of the structural arrangements in the solid state for both inorganic (20, 22, 23) and organic (5, 9, 13, and 15) molecules is determined by subtle variations in the nature of the N-substituent on the zwitterion precursor.     

Preferred bonding motif for indium aminoethanethiolate complexes: structural characterization of (Me2NCH2CH2S)2InX/SR (X = Cl, I; R = 4-MeC6H4, 4-MeOC6H4)

The metathesis reaction of InCl3 with Me2NCH2CH2SNa or the redox reaction of indium metal with elemental iodine and the disulfide (Me2NCH2CH2S)2 yield the indium bis(thiolate) complexes (Me2NCH2CH2S)2InX [X = Cl (3) and I (4)], respectively. Compounds 3 and 4 may be further reacted with the appropriate sodium thiolate salts to afford the heteroleptic tris(thiolate) complexes (Me2NCH2CH2S)2InSR [R = 4-MeC6H4 (5), 4-MeOC6H4 (6), and Pr (7)]. Reaction of 2,6-Me2C6H3SNa with 4 affords (Me2NCH2CH2S)2InS(2,6-Me2C6H3) (8), while no reaction is observed with 3, suggesting a greater reactivity for 4. All isolated compounds were characterized by elemental analysis, melting point, and Fourier transform IR and 1H and 13C{1H} NMR spectroscopies. X-ray crystallographic analyses of 3-6 show a bicyclic arrangement and a distorted trigonal-bipyramidal geometry for In in all cases. The two sulfur and one halogen (3 and 4) or three sulfur (5 and 6) atoms occupy equatorial positions, while the nitrogen atoms of the chelating (dimethylamino)ethanethiolate ligands occupy the axial positions. The metric parameters of the (Me2NCH2CH2S)2In framework were found to change minimally upon variation of the X/SR ligand, while the solubility of the corresponding compounds in organic solvents varied greatly. 1H NMR studies in D2O showed that 6 and 7 react slowly with an excess of the tripeptide l-glutathione and that the rate of reaction is affected by the pendant thiolate ligand -SR.     

Synthesis,Characteristic Spectral Studies and in Vitro Antimicrobial Activity of Organosilicon(IV) Complexes of N-(2-Hydroxynaphthalidene)-Amino Acid Schiff Bases

Fifteen new organosilicon(IV) complexes formulated as R 3 Si[2-HOC 10 H 6 CH=NCH(X)COO] and Me 2 Si[2-OC 10 H 6 CH=NCH(X)COO] (where X = H[H 2 L 1 ], --CH 2 CH(CH 3 ) 2 [H 2 L 2 ], --CH 2 CH 2 -SCH 3 [H 2 L 3 ], --CH 3 [H 2 L 4 ] and --CH(CH 3 ) 2 [H 2 L 5 ] were prepared and characterized by 1 H and 13 C NMR, IR, electronic spectral studies, and elemental analysis. All of the complexes are nonelectrolytes. The spectral studies suggested a distroted trigonal-bipyramidal geometry around the silicon atom. Antimicrobial activity screening for all of the complexes was carried out against various bacteria [ Escherichia coli, Aeromonas formicans, Pseudomonas putida-2252, and Staphylococcus aureus-740 ] and fungi [ Aureobasidium pullulans-1991, Penicillium chrysogenum-1348, Verticillium dahliae-2063, and Aspergillus niger ORS-4 ]. The complexes showed good activity.     

Ring complexes of S-nitrosothiols with CU+: a density functional theory study

The density functional theory (DFT) method B3P86/6-311+G(2df,p) has been employed to investigate the complexes formed upon interaction of Cu(+) with nitrosylated cysteine (CysNO) and its decarboxylated (H(2)NCH(2)CH(2)SNO) and deaminated (HOOCCH(2)CH(2)SNO) derivatives. Optimized structures, relative enthalpies and relative free energies have been calculated and compared. In addition, the effects of binding an H(2)O molecule to the Cu(+) centre in the resulting complexes have also been considered. It is found that the most stable complexes are formed when Cu(+) coordinates to the S-nitrosothiol via S of the SNO group. This results in dramatic lengthenings of the SN bond with concomitant shortening of the NO bond. In contrast, when Cu(+) coordinates via the nitrogen of the SNO group, a shortening of the SN bond with lengthening of the NO bond is observed. These effects are tempered by the electron donating ability of other functional groups also coordinated with the Cu(+) centre in the complexes and on the coordination state of the Cu(+) ion.     

Gramicidin A and its complexes with Cs+ and Tl+ ions in organic solvents. A study by steady state and time resolved emission spectroscopy

Gramicidin A (gr A), a linear pentadecapeptide containing four trp residues has been studied using steady state and time resolved fluorescence (at 298 K) and phosphorescence (at 77 K) in methanol (CH3OH), ethanol (C2H5OH), dimethyl sulfoxide (DMSO), 1,4-dioxane, 2-methyl tetrahydrofuran (2-MeTHF), ethanol/benzene (C2H5OH/C6H6) mixed solvent. Similar studies have also been carried out in CH3OH containing monovalent cations K+, Cs+, Tl+ and divalent cation Ca2+. Lambda(max) of fluorescence is found to be a good signature of the different forms having double helical structure [dh (1) to dh (4)] (J. Struct. Biol. 121 (1998) 123-141). Steady state and time resolved quenching studies of gr A by KI in CH3OH and DMSO and life time of the emitting singlet states of gr A support that gr A exists as a mixture of different forms of double helical (dh) structure [dh (1) to dh (4)] in CH3OH and as a random coil structure in DMSO. This study further indicates that emitting trp residue in DMSO is better shielded than that in CH3OH. Phosphorescence spectra of gr A at 77 K in CH3OH glass suggests that gr A retains a particular conformation dh (3) in this matrix. The phosphorescence spectra of gr A [conformation dh (4)] in 2-MeTHF at 77 K is further red shifted indicating that among all the dh forms, dh (4) has the emitting trp residue in most hydrophobic environment. The hydrophobicity of the emitting tryptophan environment is thus found to be in the order: dh (1)相似文献   

E.S.R., magnetic, electronic and superoxide dismutase studies of imidazolate-bridged Cu(II)-Cu(II) complexes with ethylenediamine as capping ligand

X-band E.S.R., magnetic and electronic spectra of some imidazolate-bridged homometallic complexes [(en)2Cu-R-Im-Cu(en)2](ClO4)3 where en, ethylenediamine; R-ImH, R = H imidazole (ImH); if R = CH3, 2-methylimidazole (M-ImH) and if R = C2H5, 2-ethylimidazole (E-ImH), and mononuclear complexes [(en)Cu-dien](ClO4)2 and [(en)Cu-PMDT](ClO4)2 where dien, diethylenetriamine; PMDT, pentamethyldiethylenetriamine have been described. Superoxide dismutase (SOD) activity has also been measured and compared with earlier reported complexes. In frozen solution at 77 K, the spectra show axial symmetry with a d(x2-y2) ground state. Difference in lambda(max) between mononuclear and binuclear complexes was found to be approximately 65-75 nm. Magnetic susceptibility and E.S.R. spectral measurements for all these binuclear complexes revealed that the copper(II) ions are involved in antiferromagnetic exchange interactions propagated by the imidazolate bridge.     

Spectral and structural studies of copper(II) complexes of thiosemicarbazones derived from salicylaldehyde and containing ring incorporated at N(4)-position

Mononuclear and binuclear copper(II) complexes (1-8) with two ONS donor thiosemicarbazone ligands {salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone [H2L1] and salicylaldehyde 3-tetramethyleneiminyl thiosemicarbazone [H2L2]} have been prepared and physico-chemically characterized. IR, electronic and EPR spectra of the complexes have been obtained. The thiosemicarbazones bind to metal as dianionic ONS donor ligands in all the complexes except in [Cu(HL1)2] (2) and [Cu(HL2)2] (6). In compounds 2 and 6 the ligands are coordinated as monoanionic HL- ones. The magnetic susceptibility measurements indicate that all the complexes are paramagnetic. In complex [(CuL1)2] (1), the magnetic moment value is lower than the expected spin only value. In all the complexes g(||)>g( perpendicular)>2.0023 and G values within the range 2.5-3.5 are consistent with dx2-y2 ground state. The complexes were given the formula as [(CuL1)2] (1); [Cu(HL1)2] (2); [CuL1bpy] (3); [CuL1phen] (4); [CuL1gamma-pic].2H2O (5); [Cu(HL2)2] (6); [CuL2py].3H2O (7); [CuL2bipy] (8). The structure of the compound 8 have been solved by single crystal X-ray crystallography and was found to be distorted square pyramid around copper(II) ion.     

Study of lanthanide complexes with salicylic acid by photoacoustic and fluorescence spectroscopy

Solid complexes Ln(Sal)3.H2O (Sal: salicylic acid; Ln: La3+, Nd3+, Eu3+, Tb3+) are synthesized, and their photoacoustic (PA) spectra in the UV-Vis region have been recorded. PA intensities of central lanthanide ions are interpreted in terms of the probability of nonradiative transitions. It is found that PA intensity of the ligand increases in the order of Tb(Sal)3.H2O < La(Sal3).H2O < Eu(Sal)3.H2O < Nd(Sal)3.H2O. Different PA intensities of the ligand are interpreted by comparison with the fluorescence spectra. Ternary complexes Eu(Sal)3Phen and Tb(Sal)3Phen (Phen: 1,10-phenanthroline) are synthesized. Compared with their binary complexes, PA intensity of the ligand Sal decreases for Eu(Sal)3Phen, while the reverse is true for that of Tb(Sal)3Phen. The luminescence of Eu3+ increases remarkably when Phen is introduced, and luminescence of Tb3+ decreases greatly when Phen is added. The intramolecular energy transfer and relaxation processes in the complexes are discussed from two aspects: radiative and nonradiative relaxations.