Predicting ESR Peaks in Copper (II) Chelates Having Quadrupolar Coordinating Sites by NMR, ESR and NQR Techniques: A DFT Study (original) (raw)
ESR Bonding parameter studies of single and mixed ligand complexes of copper (II)
1986
ESR and optical absorption studies are described for a number of copper(II) single and mixed ligand complexes formed with substituted salicylic acids and acetylacetone. ESR spectra of all these complexes give well-resolved spectra in DMF both at room and liquid nitrogen temperatures. The molecular orbital coefficients are estimated assuming an axial symmetry. A partial eovalency is observed in all the single ligand complexes while the in-plane ~r-bonding is as strong as the o-bonding in all the mixed ligand complexes. No regular trend is observed in the value of X (which is proportional to hyperfine constants) with the change in the overall electron withdrawing capacity of the substituent on salicylic acid, either in single ligand or in mixed ligand complexes. However, the X values for all the complexes (except in the case of b/s(acetylsalicylato)copper(II) and (acetylacetonato)-(3,5-dinitrosalicylato)copper(II)) are in agreement with the computed value of X = -3.61 for single crystals of copper-.~cetylacetonate possessing the same environment of four oxygens around copper(II).
Reactive and Functional Polymers, 1997
Chelating ion exchangers containing comparable amount of ammo groups (ethylenediamine: 2.7-2.9 mmol/g or guanidyl: OS-O.6 mmol/g) and different amount of carboxylic groups: 0.3 mmol/g-1.6 mmol/g (formed as a result of ester hydrolysis) attached to methyl methacrylate-glycidyl methacrylate-trimethylolpropane trimethacrylate (MM-GMA-TMPMA) or to methyl methacrylate-glycidyl methacrylate-trimethylolpropane triacrylate (MM-GMA-TMPA) terpolymers were synthesized and characterized. Cu@)-uptake ability of polymers containing different amino groups (ethylenediamine, guanidyl or amidoxime) and carboxylic groups with various -NH2 : -0OH ratios was determined for initial concentration of Cu@) in solution [CU@))]~~=~ x 10Y4 M and 5 x 10e5 M. EPR spectroscopy was applied to detect Cu(II) complex formation in the polymer phase as well as competition between particular amino and carboxylic groups for Cu(II) binding by structural identification of the coordination mode of the ligands. The complexes were followed and characterized by analysis of EPR parameters depending on relative content of the particular amino and carboxylic groups in the resins, on the nature of the amino groups and on relative content of Cu(LI) for particular ion exchangers. EPR spectral studies provide a unique possibility to observe the complexes in equilibrium and to determine the conditions under which donors provided by the functional groups participate in Cu(II) binding.
European Journal of Inorganic Chemistry, 2003
Dicopper complexes with N,N′-p-xylylenebis(cyclam or cyclen) and with the heteroditopic N,N′-p-xylylenebis(cyclam-cyclen) were synthesized. An X-ray study of the N,N′-p-xylylenebis(cyclen)dicopper complex showed that the copper(II) ion is five-coordinate with an H2O molecule in apical position. With this ligand, a polymeric chain was also obtained in the presence of KSCN. The terminal donor atoms of the bridging NCS− anion are coordinated in apical position to the square-pyramidal copper(II) ion. Two alternating kinds of Cu2L4+ moieties are present in the chain, the first with two N4S chromophores and the second with two N5 chromophores. EXAFS and XANES results are in agreement with a five-coordinate copper ion in the cyclen unit and a six-coordinate copper ion in the cyclam unit. Thermodynamic constants were determined by potentiometry. The existence of dinuclear Cu2L4+ species (ligand/metal ratio < 1) and mononuclear CuLHn(2+n)+ species (ligand/metal ratio > 1) were confirmed by an ESR study at variable pH. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Structural diversity in heteroleptic dipyrrinato copper(II) complexes
Inorganica Chimica Acta, 2014
Synthesis and characterization of the heteroleptic dipyrrinato complexes [Cu 2 (2-pcdpm) 2 (acac) 2 ] (1), [Cu 2 (2-pcdpm) 2 (hfacac) 2 ] (2), [Cu 3 (4-OHdpm) 2 (acac) 4 ] (3), [Cu 3 (4-OHdpm) 2 (hfacac) 4 ] (4), [Cu 2 (3-OHdpm)(acac) 3 ] (5), [Cu 2 (3-OHdpm)(hfacac) 3 ] (6), [Cu(2-OHdpm)(acac)] (7) and [Cu(2-OHdpm)(hfacac)] (8) (acac = acetylacetone; hfacac = hexafluoroacetylacetone; 2-pcdpm = 4-(2-methoxypyridyl)phenyldipyrromethene; 3-pcdpm = 4-(3-methoxypyridyl)phenyldipyrromethene; 4-pcdpm = 4-(4-methoxypyridyl)phenyldipyrromethene; 4-/3-/2-OHdpm = 4-/3-/(2-hydroxyphenyl)dipyrromethene) have been described. The complexes 1-8 have been characterized by elemental analyses, ESI-MS, IR, UV-Vis, EPR and electrochemical (CV and DPV) studies. Electronic absorption spectra of 1-8 clearly suggested that position of the absorption bands depend on the nuclearity and coordination geometry about the copper(II) centres. Structures of 1, 2, 3 and 7 have been determined by X-ray single crystal analyses. The spectral and structural studies revealed that copper(II) in 1 and 2 adopted square pyramidal geometry, whereas in 7 a square planar geometry. On the other hand in trinuclear complex 3 one copper(II) adopted square planar, while other two square pyramidal geometry. In their cyclic voltammograms, 1-6 exhibited an irreversible oxidation and two reduction waves whereas 7 and 8 displayed one oxidation and reduction wave. Variable temperature magnetic susceptibility measurements suggested paramagnetic nature of the complexes 1-3. The X-ray photoelectron spectroscopic (XPS) studies indicated that copper(II) centres in complex 3 are present in two different coordination environments. Room temperature EPR studies on 1-8 (g || > g \ > 2.003) suggested a typical d 9 copper(II) with unpaired electron lying in a d x 2 Ày 2 orbital.
Crystal structure and vibrational spectra of polyamine-copper(II) complexes
Journal of Chemical Crystallography, 1996
The structures of [Cu(en)(H2O)2]SO4 (I), [Cu(en)2](NO3)2 (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), β=105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P21/a, witha=7.978(2),b=9.982(4),c=8.218(3), β=111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P212121, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO 4 2− ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)2, (en)2 and (en) are inferred in this study.
Structure correlation study of four-coordinate copper(I) and (II) complexes
Acta Crystallographica Section B Structural Science, 2000
The geometries of four-coordinate Cu(I) and Cu(II) complexes in the Cambridge Structural Database (CSD) have been analysed systematically and compared using symmetry deformation coordinates and principal component analysis. The observed stereochemistries have been rationalised in terms of the d-electron configurations, interligand repulsion and πbonding effects. The results confirm that the majority of four-coordinate Cu(I) complexes in the CSD adopt tetrahedral geometries, and deviations from tetrahedral symmetry are caused by the presence of chelating ligands or by the incorporation of copper centres into dimeric or polymetallic structures. Four-coordinate Cu(II) complexes generally adopt geometries that are close to square planar; this is particularly evident for bis(chelate) complexes where πbonding is important. Distortions towards tetrahedral geometries are attributable to steric interactions of bulky substituents in the bidentate ligands.
Inorganic Chemistry, 1978
The single-crystal ESR spectra of copper(11)-doped bis(N-methylsalicylaldiminato)zinc(II) and (bis(3-salicylaldiminatopropyl)methylamine)zinc(II) have been recorded. Both the complexes are five-coordinate with geometries intermediate between a square pyramid and a trigonal bipyramid The g and A values of these complexes are discussed on the basis of an angular overlap model. Criteria are suggested for recognizing the ESR spectra of distorted five-coordinate complexes in diluted powders or frozen solutions.
Inorganic Chemistry, 2007
The properties of Cu(II) and Co(II) complexes with oxygen-or nitrogen-containing macrocycles have been extensively studied; however, less attention has been paid to the study of complexes containing sulfur atoms in the first coordination sphere. Herein we present the interaction between these two metal ions and two macrocyclic ligands with N 2 S 2 donor sets. Cu(II) and Co(II) complexes with the pyridine-containing 14-membered macrocycles 3,11dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L) and 7-(9-anthracenylmethyl)-3,11-dithia-7,17diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1) have been synthesized. The X-ray structural analysis of {[Co(ClO 4 )(H 2 O)(L)][Co(H 2 O) 2 (L)]}(ClO 4 ) 3 shows two different metal sites in octahedral coordination. The EPR spectra of powdered samples of this compound are typical of distorted six-coordinated Co(II) ions in a high-spin (S ) 3/2) configuration, with the ground state being S ) 1/2 (g 1 ) 5.20, g 2 ) 3.20, g 3 ) 1.95). The EPR spectrum of [Cu(ClO 4 )(L)](ClO 4 ) was simulated assuming an axial g tensor (g 1 ) g 2 ) 2.043, g 3 ) 2.145), while that of [Cu(ClO 4 )(L1)](ClO 4 ) slightly differs from an axial symmetry (g 1 ) 2.025, g 2 ) 2.060, g 3 ) 2.155). These results are compatible with a Cu(II) ion in square-pyramidal coordination with N 2 S 2 as basal ligands. Single-crystal EPR experiment performed on [Cu(ClO 4 )(L1)](ClO 4 ) allowed determining the eigenvalues of the molecular g tensor associated with the copper site, as well as the two possible orientations for the tensor. On the basis of symmetry arguments, an assignment in which the eigenvectors are nearly along the Cu(II)−ligand bonds is chosen.
Polyhedron, 2002
Stabilities of the mixed-ligand complexes of Cu 2 + ion with N, N,N%,N¦,N¦-pentamethyldiethylenetriamine [N,N,N%,N¦,N¦-pentamethyl-{bis(2-aminoethyl)amine}, Me 5 dien] as a primary ligand and a-alaninehydroxamic acid [2-amino-N-hydroxypropanamid, a-Alaha] or b-alaninehydroxamic acid [3-amino-N-hydroxypropanamid, b-Alaha] as a secondary ligand L and their absorption and EPR spectra at various pH values are reported. The visible spectra exhibit a characteristic red shift and a shoulder at lower energies indicating a five-coordinate structure of the formed complexes. The change of the EPR spectral parameters as a function of pH reflects two modes of an equatorial-axial chelation by the aminohydroxamic acid ligand L in the [Cu(Me 5 dien)(HL)] 2 + and [Cu(Me 5 dien)(L)] + species.
Inorganic Chemistry, 1980
Cr-P Cr-CO(trans) C-O(trans) Cr-CO(cis) C-O(cis) fuc-Cr(C0) , (PEt 3) 3 2.429 [S] 1.829 [ a ] 1.162 [ 3 ] Cr(C0) 5(PPh3) 2.422 (1) 1.845 (4) 1.154 (5) 1.880 [ l l ] 1.150 [5] cis-Cr(CO), (PH,), l 6 2.349 (2) 1.847 (4) 1.162 (6) 1.914 (7) 1.113 (33) fac-Cr(CO), (PH,), 2.346 (4) 1.84 (1) 1.16 (1) cisCr(CO) (PH 3) ' 2.338 (4)a 1.817 (7) 2.282 (4)b Cr(CO), [P(OPh),l' 2.309 (1) 1.861 (4) 1.136 (6) 1.896 [ 6 ] 1.131 [3] 1.140 [6] trans-Cr(CO),[ P(OPh),] " 2.252 (1) 1.878 [ 4 ] a Trans to CO. Trans to another phosphine ligand. [average = 2.429 [8] A]-represent the longest chromium-(0)-phosphorus bonds characterized to date (see Table VI). Of particular interest is a comparison with the closely related species ~u c-C~(C O) , (P H ,) , ,~ in which the Cr-P distances average 2.346 (4) A. The longer Cr-P distances infuc-Cr-(CO),(PEt,), suggest a weakening of the Cr-P bonds caused by steric interactions between the adjacent PEt, ligands. The short Cr-CO bond lengths [1.829 [8] 8, (average)] and long C-0 bond lengths [ 1.162 [3] 8, (average)] in fuc-Cr-(CO),(PEt,), are consistent with strong d,-x*(CO) backdonation and suggest that PEt, behaves essentially as a cr-donor ligand, with little or no r-acceptor capability. Registry No. f a~-C r (C 0)~(P E t~)~, 73505-52-9; Nat[Mn(C0)5-], 13859-4 1-1, Supplementary Material Available: Tables of structure factors and data processing formulas (10 pages). Ordering information is given on any current masthead page. Correspondence Effects of Planar and Tetrahedral Distortions on the ESR Parameters of Bis(salicylaldiminato)copper(II) Complexes
Polyhedron, 2013
Three copper (II) complexes of type [Cu(L) 2 (NCX)]ClO 4 , 1-3, (L = N,N-dimethyl,N 0-benzyl-1,2-diaminoethane and X = O, S and Se) were synthesized and characterized on the basis of microanalytical, spectroscopic and molar conductance. An X-ray diffraction study of [Cu(L) 2 (NCO)]ClO 4 (1) reveals that the copper (II) center located in a distorted square pyramidal environment through coordination of four amine N atoms and a N atom of the terminal NCO À. Density functional theory (DFT) calculations were performed to understand the linkage isomerism of NCX À ligand from a theoretical point of view, to study the electronic structure of the complexes and the relative stabilities of the Cu-NCX/Cu-XCN isomers. DFT computational results buttressed the experimental observations indicating that the Cu-NCX isomer is more stable than Cu-XCN linkage isomer. Complexes 1 and 2 exhibit solvatochromism as evidenced from visible study in different solvents.
Organic Magnetic Resonance, 1984
ESR and optical absorption studies are described for a number of copper(1I) chelates with aliphatic polyamines, exhibiting both square pyramidal and square bipyramidal coordination around the copper ion. The complexes studied were bis(N,N'-dimethylethylenediamine)copper(II) sulphate tetrahydrate, bis(N,N'-diethylethylenediamine)copper(II) nitrate, diaquosulphato(N,N,W,N'-tetramethylethylenediamine)copper(II) hydrate, dinitrato(N,N,N',N'-tetramethylethylenediamine)copper(II), dichloro(NJV,N',N'-tetramethy1ethylenediamine)copper (n) and dithiocyanato(N,NJV',iV-tetramethylethylenediamine)copper(II). The ESR measurements were carried out in methanol, dimethyl sulphoxide, dimethylformamide and pyridine, at room and liquid nitrogen temperatures. The molecular orbital coefficients were estimated assuming an axial symmetry. The parameter x, proportional to the hyperfine constants shows a variation with the solvent for all these complexes. The x values in solution are lower than the corresponding average x values reported in the solid state for each complex. The solvent effect and the influence of 4s character in the ground state are discussed. The x values, either calculated or reported, for a number of copper complexes for [40], [30, N], [ZO, 2N], [0,3N] and [4N] environments around copper(Il) are presented.
Inorganic Chemistry, 1996
The tripodal tetramine ligands N(CH 2 CH 2 CH 2 NH 2) 3 (trpn) and N[(CH 2 CH 2 CH 2 NH 2) 2 (CH 2 CH 2 NH 2)] (332) react with Cu(NO 3) 2 ‚3H 2 O in water to give light blue copper(II) complexes. These were characterized by X-ray crystallography to be the square-pyramidal binuclear Cu(II) species [Cu(trpn)(NO 3)] 2 (NO 3) 2 and [Cu(332)(NO 3)] 2-(NO 3) 2 ‚2H 2 O. Selected crystallographic details are as follows, respectively: formula C 18 H 48 Cu 2 N 12 O 12 , C 16 H 48-Cu 2 N 12 O 14 ; M) 751.74, 759.72 Da; both triclinic; both P1 h; a) 8.4346(8), 8.446(4) Å; b) 9.0785(9), 8.744(3) Å; c) 11.9310(12), 12.007(3) Å; R) 94.50(1), 102.68(2)°;) 103.56(1), 94.79(3)°; γ) 117.42(1), 117.69-(4)°; V) 769.7(5), 748.2(13) Å 3 ; both Z) 1; R) 4.16, 4.00; R w) 11.34, 6.74 for 2887 (I g 2σ(I)), 2457 (F o 2 g 3σ(F o 2)) structure factors and 199, 209 refined parameters. The binuclear complex dications exhibit a squarepyramidal coordination geometry around the copper atoms. Three amine functions (one tertiary and two primary) are coordinated to one copper atom and the remaining primary amine arm bridges to the second copper center. Potentiometric and visible spectrophotometric studies show that a protonated square-pyramidal [Cu(HL)(H 2 O) 2 ] 3+ cation (L) trpn, 332, 322 (322) N[(CH 2 CH 2 CH 2 NH 2)(CH 2 CH 2 NH 2) 2 ])) predominates in the intermediate pH region, in contrast to the established trigonal-bipyramidal structure of the tren (tren) tris(2-aminoethyl)amine)) complex of Cu(II). Each [Cu(HL)(H 2 O) 2 ] 3+ has one protonated uncoordinated ligand arm which explains the formation of the binuclear species at neutral pH.
Transition Metal Chemistry, 2009
An EPR method involving measurement of halffield transitions was applied to determine the intermolecular Cu-Cu distances in copper(II)-carboxylate complexes with biologically important ligands. The experimental powder EPR spectra are composed of allowed (DM S = ±1) transitions centered at *3,200 Gauss and of weak intensity, nominally forbidden, half-field (DM S = ±2) peaks observable at *1,600 Gauss. Values of the average interspin distance for each complex were determined from the ratios of integrated allowed and forbidden peak areas using each of several methods. The calculated interspin distances were correlated with the copper-copper distances experimentally obtained by X-ray crystallography. The distances determined from the EPR spectra agree well with the X-ray determined values when the crystallographic value for one member of a series is used to calibrate the series. Less satisfactory agreement is found when methods based on Cu-spin-label systems are used.
Journal of Organometallic Chemistry, 2011
a b s t r a c t DFT calculations have been performed for some Cu(III)-alkyl complexes. Complexes 1e19 were optimized to the square planar (sq) geometry and observed no imaginary frequencies. Although formally copper adopts d 8 configuration (Cu(III)) in all the complexes, the Natural Population Analysis (NPA) revealed that the copper actually in d 10 (Cu(I)) configuration, Bond order calculation suggested that the Cu(III)eEt trans bond gets more bond order in the presence of poor p-acidic co-ligand (probe ligand). Relatively smaller bond order was calculated for Cu(III)eMe cis bond than Cu(III)eEt trans bond and therefore Cu(III)eEt trans bond is the strongest bond in all the complexes. Calculated less Chemical hardness (h) of complexes 1e19 suggested that all these complexes are less stable in nature. Energy Decomposition Analysis (EDA) revealed that the Cu(III)eEt trans bond is relatively more stable than the Cu(III)eMe cis and Cu(III)eL (L ¼ co-ligand/probe ligand) bonds. And also the Cu(III)ealkyl (Cu(III)eMe cis and Cu(III)eEt trans ) bond in complexes 1e17 is more of ionic in nature. However, Cu(III)eEt trans bond is relatively more ionic than Cu(III)eMe cis bond.
Polyhedron, 2012
The oxido-pincer ligand pydotH 2 (2,6-bis(1-hydroxy-1-o-tolyl-ethyl-g 2 O,O 0 )pyridine) forms two different Cu II containing complexes when prepared from anhydrous CuCl 2 . A combination of EPR spectroscopy and EXAFS allowed to structurally characterise the light-green dimer of the formula [(pydotH 2 )CuCl(l-Cl) 2 ClCu(pydotH 2 )] and the penta-coordinate olive-green monomer [(pydotH 2 )CuCl 2 ]. The molecular entities imply that the ligand remains protonated upon coordination. When dissolved in DMF both compounds form monomeric species [(pydotH 2 )CuCl 2 (DMF)] which could be characterised in detail by EPR, UV-Vis/NIR spectroscopy and electrochemical measurements. The assignments were supported by comparison with Cu II complexes of the related ligands 2,6-bis(hydroxymethyl)pyridine (pydimH 2 ) and 2,6bis(1-hydroxy-1-methyl)pyridine (pydipH 2 ).