Chan-Cheng Su

Electronic and bonding properties of acetylacetonato copper(II) complexes. Molecular structure of [Cu(Acetylacetonato)(1,10-phenanthroline)(ClO4)(0.5CH3CN)]

Abstract The preparation and characterization of mixed ligand complexes, [Cu (acac)(NN)(ClO 4 )] (acac = acetylacetonate, NN = N , N , N ′, N ′-tetramethylethylenediamine, 2,2′-bipyridine, 1,10-phenanthroline (phen), and neocuproine), are reported. The structure of [Cu(acac)(phen)(ClO 4 )(0.5CH 3 CN)] determined from three-dimensional X-ray diffraction data comprises discrete square pyramidal [Cu(acac)(phen)(ClO 4 )] and [Cu (acac)(phen)(CH 3 CN)](ClO 4 ) units, with the perchlorate or the CH 3 CN on the apex. The CH 3 CN is coordinated in an unusual bent mode with a CuNC angle of 129.2(9)°. Analysis of the electronic spectra of the complexes suggests the sequence of d orbitals as d xy ⪢ d z 2 > d x 2 y − y 2 ∼ d xz > d yz . In square pyramidal complexes, acetylcetonate ligands are π donors whilst heterocyclic diimines are not participated in π interactions.

Bonding properties of penta-coordinate CuII-N chromophores: structures and electronic spectra of copper(II) complexes of tris(2-aminoethyl)amine (tren). Molecular structures of [Cu(tren)(N-acetylhistamine)](ClO4)2 and [Cu(tren)(2-methylimidazole)](ClO4)2

Abstract Tris(2-aminoethyl)aminecopper(II) perchlorate complexes, [Cu(tren)L](ClO4)2 [tren is tris(2-aminoethyl)amine and L are neutral N-donor ligands including imidazoles, pyridines and amines], have been synthesized and characterized. The X-ray crystal structures of [Cu(tren)(achmH)](ClO4)2 (1) and [Cu(tren)(2MImH)](ClO4)2 (2) (achmH = N-acetylhistamine; 2MImH = 2-methylimidazole) have been determined. Their structures consist of discrete perchlorate anions and distorted trigonal-bipyramidal [Cu(tren)(N-donor)]2+ cations with the three primary amine groups of the tren ligand forming the equatorial plane, where one of the equatorial angles is larger than the other two and the CuN opposite the largest equatorial NCuN angle is significantly longer than the other two. Electronic and EPR spectra are reported for these complexes. The LF spectra are analysed in trigonalbipyramidal symmetry with the Jahn-Teller effect being considered in the excited state and the effect of geometric distortions. The d-orbitals are assigned in a sequence of dz2 >> dx2-y2 > dxy > dxz ≈ dyz. The bonding properties of the CuN5 chromophores are elucidated and discussed with reference to the electronic structures of the complexes, suggesting no π-interaction in the axial CuN bonds.

Electronic and bonding properties of mixed ligand pyridine-2,6-dicarboxylate copper(II) complexes: Molecular structures of [Cu(4-dimethylaminopyridine)(pyridine-2,6-dicarboxy lato)] and [Cu(N-methylimidazole)(pyridine-2,6-dicarboxylato)(0.5H2O)]

Abstract Mixed-ligand pyridine-2,6-dicarboxylatocopper(II) complexes, [Cu(dipic)(L)] [dipic = pyridine-2,6-dicarboxylate, L = imidazole, N-methylimidazole (nmim), 4-methylimidazole, pyridine, 4-methylpyridine, 4-aminopyridine, 4-dimethylaminopyridine(4dmapy) and NH3 · H2O], have been synthesized and characterized by elemental analyses, and UV—vis, IR and EPR spectroscopic measurements. Molecular structures of [Cu(dipic)(4dmapy)] (1) and [Cu(dipic)(nmim)(H2O)0.5] (2) have been determined by X-ray diffraction methods. Complex 1 is square planar and 2 comprises both square pyramidal [Cu(dipic)(nmim)(H2O)] and square planar [Cu(dipic)(nmim)] units. The equatorial heterocyclic unidentate ligands are nearly co-planar with the CuN2O2 coordination plane: 1.3° for 1, 6.8° and 13.9° for the square plane and square pyramid, respectively, of 2. The structures of other heterocyclic complexes are suggested to be square planar based on their spectroscopic data. The sequence of d orbitals was assigned as dx2−y2 ≫ dxz > dxy dyz > dz2 for the square planar complexes and dx2−y2 ≫ dz2 > dx > dxy > dyz for the square pyramidal NH3 complex. The significant rise in energy of the dxz orbitals suggests that the central pyridine nucleus of the dipicolinate ligand and the heterocyclic unidentate ligands are π-donors. This is attributable to ionic bonding effects.

Bonding properties of copper(II)—N chromophores: Molecular and electronic structures of copper(II) complexes containing ethylenediamine and heterocyclic diimine ligands

Abstract Mixed ligand ethylenediaminecopper(II) perchlorate complexes, [Cu(en)LL (H2O)](ClO4)2, en = ethylenediamine and LL stands for 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), and N,N,N′,N′-tetramethylethylenediamine (tmen), have been prepared and characterized by elementary analyses, and electronic, vibrational, and EPR spectroscopic measurements. The crystal and molecular structures of [Cu(en)(bipy) (H2O)](ClO4)2 (1) and [Cu(en)(phen)(H2O)](ClO4)2 (2) have been determined from single-crystal, three-dimensional X-ray diffraction data. Both complexes, crystallized in triclinic P 1 − group, contain discrete copper(II) cations having a CuN4 basal plane and a H2O on the apex. A similar structure was suggested for [Cu(en)(tmen)(H2O)](H2O)](ClO4)2 (3). The single-crystal polarized electronic spectra of 1 and 2 were measured and resolved into a set of three Gaussian component peaks for each spectrum. Gaussian analyses performed on the crystal and the powder LF bands for these complexes yielded a one-electron orbital sequence dxy > dz2 > dx2−y2 > dyz > dxz. Bonding properties of the bidentate ligands are elucidated suggesting virtually no π-interactions between the heterocyclic diimine ligands and the central copper(II) ion in these ethylene-diamine complexes.

Electronic and bonding properties of mixed-ligand copper(II) complexes of N-(2-picolyl)picolinamide (pmpa). X-ray crystal structures of [Cu(pmpa) (4-methylimidazole)(H2O)](H2O)(ClO4) and [Cu(pmpa)(4-methylpyridine)(H2O)] (H2O)(ClO4)

Abstract Mixed-ligand N -(2-picolyl)picolinamidocopper(II) complexes, [Cu(pmpa)(L)(X) · n H 2 O] [pmpa = N -(2-picolyl)picolinamide anion; L = imidazole ( n = 0, o or 2), N -methylimidazole ( n = 0 or 1), 4-methylimidazole (4MImH) ( n = 0 or 2), pyridine ( n = 0), 2-methylpyridine ( n = 0), 3-methylpyridine ( n = 0), 4-methylpyridine (4Mpy) ( n = 2), and NH 3 ( n = 2); X = ClO 4 − or BF 4 − ], have been synthesized and characterized by elemental analyses, and electronic, vibrational, and EPR spectroscopic measurements. Molecular structures of [Cu(pmpa)(4MImH)(H 2 O)](H 2 O)](H 2 O)(ClO 4 ( 1 ) and [Cu(pmpa)(4Mpy)(H 2 O)](H 2 O)(ClO 4 ) ( 2 ) have been determined by X-ray diffraction methods. Both complexes are square pyramidal with the pmpa and the heterocyclic unidentate ligands forming the basal plane and a H 2 O molecule on the apical position. The dihedral angles of the heterocyclic unidentate nucleus and the CuN 4 basal plane are 79.3° for 1 and 74.5° for 2 . The structures of other pmpa complexes are suggested to be square pyramidal or square planar based on their spectroscopic data. The sequence of d orbitals is assigned as d x 2 − y 2 ⪢ d z 2 > d yz > d xy > d xz for the square pyramidal complexes and d x 2 − y 2 ⪢ d yz > d xy > d xz > d z 2 for the square planar complexes. The significant rise in energy of the d yz orbital suggests that the central amido of the pmpa ligand is a strong π-donor.

Bonding properties of copper(II)-imidazole chromophores: electronic and molecular structure of tetrakis(imidazole)bis(tetrafluoroborato)copper(II)bis(hexamethylphosphoramide)

SummaryThe crystal and molecular structure of [Cu(HIm)4(BF4)2]-2hmpa (HIm=imidazole; hmpa=hexamethylphosphoramide) has been determined using three-dimensional x-ray diffraction data. The CuII ion is coordinated centrosymmetrically by four imidazole ligands forming a basal plane, mean Cu−N 2.005 Å, and by two tetrafluoroborate anions on the z axis, mean Cu−F 2.506 Å. The four imidazole ligands are inclined at 64.6±0.5° to the CuN4 coordination plane. The discrete CuII complexes and hexamethylphosphoramide molecules are interconnectedvia hydrogen bonding between the imidazole N−H group and hmpa oxygen atom. The hmpa has a tetrahedral configuration around P with P=O 1.489 Å and mean P−N 1.629 Å. The deconvoluted d-d absorptions of the title compound yield an orbital sequence: dx2−y2>dz2>dxy>dyz=dxz. The properties of the Cu-imidazole bonds are discussed with reference to the electronic structures of the chromophores of tetrakis(imidazole)copper(II) complexes having effective local symmetriesD4h andD2h.

Spectroscopic and electronic properties of mixed ligand aminoacidatocopper(II) complexes: Molecular structure of [Cu(4,7-dimethyl-1,10-phenanthroline)(l-phenylalaninato)](ClO4)

Abstract Mixed-ligand aminoacidatocopper(II) complexes of the types, [Cu( l -phe)(NN)](ClO4)·nH2O [ l -phe= l -phenylalaninato; NN=2,2′-bipyridine (n=2), 1,10-phenanthroline (n=2), and 4,7-dimethyl-1,10-phenanthroline (dmphen, n=0)], [Cu(gly)(NN)](ClO4)·nH2O [gly=glycinato; NN=2,2′-bipyridine (n=1), 1,10-phenanthroline (n=0), neocuproine (n=0), and ethylenediamine (n=2)], and [Cu( l -ala)(NN)](ClO4)·nH2O [ l -ala= l -alaninato; NN=2,2′-bipyridine (n=0), 1,10-phenanthroline (n=1), and neocuproine (n=2)], have been synthesized and characterized by elemental analyses, and IR, UV–Vis, CD, and EPR spectroscopic measurements. The molecular structure of [Cu( l -phe)(dmphen)](ClO4) (1) has been determined by three-dimensional X-ray diffraction data. Complex 1 consists of discrete perchlorate anions and square planar cationic copper complexes. Based on the spectroscopic data, the structures of the complexes are either square pyramidal or square planar in solid state, whereas they are square pyramidal in solution. The sequence of d orbitals was assigned as dxy≫dz2>dx2−y2>dyz>dxz for the solution species as deduced from the Gaussian resolved electronic absorption and CD spectroscopic data. Both aminoacidato and heterocyclic diimine ligands do not participate in π-interactions in these complexes.

Molecular and electronic structures of bis(dipicolylamine)copper(II) perchlorate and bis[2-(2-pyridylethyl)picolylamine]copper(II) perchlorate

The geometric isomers of bis(dipicolylamine)copper(II) perchlorate, [Cu(dipica)2](ClO4)2, and bis[2-(2-pyridylethyl)picolylamine]copper(II) perchlorate, [Cu(pepica)2](ClO4)2, have been prepared and their molecular structures determined by X-ray diffraction methods. The copper atom of cis-fac-[Cu(dipica)2](ClO4)2, is six coordinate with an amine nitrogen and a pyridyl group of each facial dipica ligand forming a cis coordination plane, and the remaining pyridyl nuclei on the axial sites completing a distorted octahedral structure. The mixed trans-fac-  &  square-pyramidal-[Cu(dipica)2](ClO4)2 comprises discrete hexacoordinate and pentacoordinate cations. The distorted trans-facial octahedral cation has two picolyl chelates in the equatorial plane and two slightly longer axial pyridyl groups. In the square-pyramidal cation, the basal plane is formed by a meridional tridentate dipicia and a pyridyl of another bidentate dipica ligand, of which the amine group is bound at the apex. The copper ion of trans-fac-[Cu(pepica)2](ClO4)2 is bound by two picolyl chelates in the equatorial plane and two elongated axial pyridyl groups. The electronic structures of these complexes are deduced based on their electronic and e.p.r. spectra. The bonding properties and the formation of the geometric isomers are elucidated.

Bonding properties of Cu(II)N chromophores: preparation, structure and spectroscopic properties of mixed ligand 2,2′:6′,2″-terpyridine copper(II) complexes. Molecular structures of [Cu(terpyridine)(4-methylimidazole)(H2O)(BF4)] (BF4) and [Cu(terpyridine)(3-methylpyridine)(BF4)2)]

Abstract Mixed ligand 2,2′:6′,2″-terpyridine copper(II) complexes of the Cu(terpy)L(BF4)2·nH2O type, where terpy stands for terpyridine, and L for imidazole (n = 1), N-methylimidazole (n = 1), 4-methylimidazole (n = 1), benzimidazole (n = 1), pyridine (n = 0), 3-methylpyridine (n = 0), 4-methylpyridine (n = 1), and NH3 (n = 0), have been synthesized and characterized by elemental analyses, and electronic, vibrational, and EPR spectroscopic measurements. The X-ray crystal structures of [Cu(terpy)(4MImH)(H2O) (BF4)](BF4) (1) and [Cu(terpy)(3Mpy)(BF4)] (2) (4MImH = 4-methylimidazole; 3Mpy = 3-methylpyridine) have been determined from three-dimensional X-ray diffraction data. Both complexes comprise [4+1 + 1] copper units where the terpy and the unidentate N-donor ligand bind to the central copper ion forming a square plane. The CuN bond lengths along the unidentate ligand are considerably shorter than the others. The dihedral angle between the CuN4 coordination plane and the imidazole nucleus in 1 is 85.3°; the corresponding angle between the CuN4 plane and the pyridine nucleus in 2 is 66.2°. Similar structures with a CuN4 coordination plane are proposed for other complexes based on spectroscopic data. The sequence of the d orbitals has been deduced from Gausian analysis of the LF spectra as dx2−y2 > dz2 > dxy > dyz > dxz, where x axis is along the CuN(unidentate) on the CuN4 plane. The bonding properties of these complexes are elucidated and discussed with reference to the electronic structures.

Electronic and bonding properties of mixed-ligand copper(II) complexes of N-(2-pyridylethyl)picolinamide (pepa). Molecular structures of [Cu(pepa)(3-methyl-pyridine) (H2O)](ClO4), [Cu(pepa)(4-methylpyridine) (H2O)](ClO4) and [Cu(pepa)(4-methylimidazole) (H2O)](H2O)(ClO4)

Abstract Mixed-ligand N-(2-pyridylethyl)picolinamidocopper(II) complexes, Cu(pepa)(L)(H2O)n(ClO4) [pepa = N-(2-pyridylethyl)picolinamide anion; L = imidazole (n = 0), N-methylimidazole (n = 1), 2-methylimidazole (n = 1), 4-methylimidazole (4MImH, n = 2), 3-methylpyridine (3Mpy, n= 1 and 2), and 4-methylpyridine (4Mpy, n = 1 and 2)], have been synthesized and characterized by elemental analyses, and electronic, vibrational and EPR spectroscopic measurements. Molecular structures of [Cu(pepa)(3Mpy)(H2O)](ClO4) (1), [Cu(pepa)(4Mpy)(H2O)](ClO4) (2) and [Cu(pepa)(4MImH)(H2O)(ClO4) (3) have been determined by X-ray diffraction methods. The structures of these complexes are square pyramidal with the pepa and a heterocyclic unidentate ligand forming the basal plane and an H2O molecule on the apical position. The dihedral angles of the heterocyclic unidentate nucleus and the CuN4 basal plane are 74.3° for 1, 66.8° for 2 and 77.7° for 3. The structures of other pepa complexes are suggested to be square pyramidal based on their spectroscopic data. The sequence of d orbitals was assigned as dx2−y2 ⪢ dz2 > dyz > dxy > dxz for the square pyramidal complexes. The significant rise in energy of the dyz orbital suggests that the central amido of the pepa ligand is a strong π-donor.