Addison Parameter Research Articles

Experimental and Theoretical Survey of Intramolecular Spodium Bonds/σ/π-Holes and Noncovalent Interactions in Trinuclear Zn(II)-Salen Type Complex with OCN- Ions: A Holistic View in Crystal Engineering.

In this work, one new centrosymmetric trinuclear Zn(II) complex 1, [{(OCN)Zn(L)}2Zn], using a salen-type ligand (H2L) in the presence of OCN- was synthesized and characterized via elemental, spectral, SEM-EDX, and single-crystal X-ray diffraction (SCXRD) study. In 1, SCXRD reveals two different stereochemical environments of zinc metal ions; one terminal Zn(II) center adopts square pyramidal geometries with the Addison parameter (τ) 0.095, and the central Zn(II) is tetracoordinated tetrahedral geometry. This article provides evidence of the significance and presence of spodium bonds (SpBs) in solid-state crystal structures involving a pseudotetrahedral environment of the central Zn-atom. X-ray structures reveal intramolecular Zn···O SpBs caused by the methoxy (-OCH3) substituent O-atom adjacent to the coordinated phenoxy O-atom. These noncovalent interactions have been thoroughly studied using density functional theory calculations at the RI-BP86[2]-D3[3]/def2-TZVP level of theory that characterizes the nature of SpBs, including the Baders quantum theory of atoms-in-molecules "QTAIM", molecular electrostatic potential (MEP) surface, and noncovalent index plot (NCI). In addition, a unique complex-isomer-based theoretical model has been vividly employed to estimate the SpBs energy in the complex. Natural bond orbital (NBO) analysis also tries to establish the differentiation between σ-hole and π-hole SpBs' natures more authentically. The complex energy frameworks were used to investigate noncovalent interactions. To better understand the different intermolecular interactions, we conducted a Hirshfeld surface, which revealed N···H (15.4%) and O···H (9.1%) contacts and Zn···O (5.1%) (SpBs).

Cation-/Ligand-Induced Solvent-Assisted Transformations of Zn(II) and Cu(II) Complexes Featuring Single-Pocket Multidentate Chelating Members

A new family of single-pocket metal complexes bearing O,N,O-tridentate and O,N-bidentate chelating members {Cu, 1b (P21/n); Ni, 1c (C2/c); Mn, 1d (I2/a); Cu, 2b; and Ni, 2c (both P21/c)}, starting from synthesized and fully characterized Zn(II) (1a; I2/a) and Cu(II) (2a; C2) precursors, were conveniently prepared via cation-induced solvent-assisted and ligand-induced solvent-assisted transformations. Herein, we show multistep solvent-assisted transformations from cis-1a → trans-1b → cis-1c → cis-1d, as well as all-trans 2a → 2b → 2c. All processes are one-way irreversible, as substantiated by thermodynamic aspects (enthalpies based on Gibbs free energies) derived from density functional theory calculations. On the other hand, complex 2a′ (C2/c; a polymorphic form of 2a) was obtained through a routine synthetic procedure. The compounds have been established by various spectroscopic techniques (infrared, UV–vis, ESI-MS, 1H, and 13C NMR), elemental analysis, and X-ray crystallography. Single-crystal X-ray studies reveal that complexes 1a–d exhibit a pseudo-octahedral geometry around each metal center, with 2a displaying a four-coordinate seesaw geometry Cu(II) sphere (Addison parameter; τ = 0.42), while 2a′ (τ = 0.00), 2b (τ = 0.00), and 2c (τ = 0.00) possess a perfect square-planar configuration around each metal center. Furthermore, distortion is stabilized by the presence of peripheral O-donor atoms from the bulky −OMe group, and by virtue of its size, increased bond lengths and angles are accommodated. Ligand substitution induced coordination geometry transformation from quasi-square-planar 2a to perfect square-planar 2b. Assessment of the metric parameter shows that the distances between the two Cu–Omethoxy are all largely positive due to Jahn–Teller distortion, indicating an unprecedented tetragonal bipyramidal geometry in 1b.

Synthesis, structural characterization and thermal properties of a new copper(II) one-dimensional coordination polymer based on bridgingN,N′-bis(2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine and dicyanamide ligands

The design and synthesis of polymeric coordination compounds of 3d transition metals are of great interest in the search for functional materials. The coordination chemistry of the copper(II) ion is of interest currently due to potential applications in the areas of molecular biology and magnetochemistry. A novel coordination polymer of Cu(II) with bridging N,N'-bis(2-hydroxyphenyl)-2,2-dimethylpropane-1,3-diamine (H2L-DM) and dicyanamide (dca) ligands, catena-poly[[[μ2-2,2-dimethyl-N,N'-bis(2-oxidobenzylidene)propane-1,3-diamine-1:2κ(6)O,N,N',O':O,O']dicopper(II)]-di-μ-dicyanamido-1:2'κ(2)N(1):N(5);2:1'κ(2)N(1):N(5)], [Cu2(C19H20N2O2)(C2N3)2]n, has been synthesized and characterized by CHN elemental analysis, IR spectroscopy, thermal analysis and X-ray single-crystal diffraction analysis. Structural studies show that the Cu(II) centres in the dimeric asymmetric unit adopt distorted square-pyramidal geometries, as confirmed by the Addison parameter (τ) values. The chelating characteristics of the L-DM(2-) ligand results in the formation of a Cu(II) dimer with a double phenolate bridge in the asymmetric unit. In the crystal, the dimeric units are further linked to adjacent dimeric units through μ1,5-dca bridges to produce one-dimensional polymeric chains.

Large and negative magnetic anisotropy in pentacoordinate mononuclear Ni(ii) Schiff base complexes.

A series of pentacoordinate Ni(ii) complexes of the general formula [Ni(L5)] () with various pentadentate Schiff base ligands H2L5 (originating in a condensation of aromatic ortho-hydroxy-aldehydes and aliphatic triamines) was synthesized and characterized by X-ray structure analysis and magnetometry. The alternations of substituents on the H2L parent ligand resulted in the complexes with the geometry varying between the square-pyramid and trigonal-bipyramid. In the compounds whose chromophore geometry is closer to a trigonal-bipyramid, a large and negative uniaxial anisotropy (D = -64 cm(-1)) was identified. Moreover, the simple linear expression for the axial zero-field splitting (ZFS) parameter, D/cm(-1) = 32.7(4.8) - 151(10)τ, was proposed, where τ (in degrees) stands for the Addison parameter. The results of magnetic analysis were also supported by ab initio CASSCF/NEVPT2 calculations of the ZFS splitting parameters D and E, and g tensors. Despite large and negative D-values of the reported compounds, slow relaxation of magnetization was not observed either in zero or non-zero static magnetic field, thus no single-molecule magnetic behaviour was detected.

Synthesis and spectral characterization of mono- and binuclear copper(II) complexes derived from 2-benzoylpyridine-N4-methyl-3-thiosemicarbazone: Crystal structure of a novel sulfur bridged copper(II) box-dimer

Mononuclear and binuclear copper(II) complexes of 2-benzoylpyridine-N4-methyl thiosemicarbazone (HL) were prepared and characterized by a variety of spectroscopic techniques. Structural evidence for the novel sulfur bridged copper(II) iodo binuclear complex is obtained by single crystal X-ray diffraction analysis. The complex [Cu2L2I2], a non-centrosymmetric box dimer, crystallizes in monoclinic C2/c space group and it was found to have distorted square pyramidal geometry (Addison parameter, τ=0.238) with the square basal plane occupied by the thiosemicarbazone moiety and iodine atom whereas the sulfur atom from the other coordinated thiosemicarbazone moiety occupies the apical position. This is the first crystallographically studied system having non-centrosymmetrical entities bridged via thiolate S atoms with Cu(II)I bond. The tridentate thiosemicarbazone coordinates in mono deprotonated thionic tautomeric form in all complexes except in sulfato complex, [Cu(HL)(SO4)]·H2O (1) where it binds to the metal centre in neutral form. The magnetic moment values and the EPR spectral studies reflect the binuclearity of some of the complexes. The spin Hamiltonian and bonding parameters are calculated based on EPR studies. In all the complexes g||>g⊥>2.0023 and the g values in frozen DMF are consistent with the dx2-y2 ground state. The thermal stabilities of some of the complexes were also determined.

Synthesis and characterization of four dicyanamide bridged copper(II) complexes with N2O donor tridentate Schiff bases as blocking ligands

Four copper(II) complexes [Cu(L1)(dca)]n (1), [Cu(L2)(dca)(H2O)]2 (2), [Cu(L3)(dca)]n (3) and [Cu(L4)(dca)]n (4), where HL1=2-[(2-aminoethylimino)methyl]-4-nitrophenol, HL2=2-[(2-(methylamino)ethylimino)methyl]-4-nitrophenol, HL3=2-[(2-(dimethylamino)ethylimino)methyl]-4-nitrophenol and HL4=2-[(2-(diethylamino)ethylimino)methyl]-4-nitrophenol are tridentate Schiff base ligands, were synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. Complex 1 and 4 are 1D helical, complex 2 is dimeric and complex 3 is 1D linear chain. X-ray single crystal structure analyses reveal that in complexes 1, 2 and 4, dicyanamide (dca) anions act as a purely μ-1,5-bridging ligand whereas in case of complex 3, two consecutive dca units serve as 1,3-bridging ligand while the third one exhibits end-to-end 1,5-bridging mode. Copper(II) centers in case of two complexes (1 and 3) exhibit square pyramidal geometry as depicted by Addison parameter (τ) values whereas metal centers of complexes 2 and 4 depict distorted octahedral and square pyramidal geometry respectively. The role of weak forces like lone pair⋯π/π⋯π interactions in influencing the self-assembly process appears to be of importance. Such types of interactions leading to supramolecular network in the four complexes are described here.

Counter anion modulated variation of denticity of NNO donor Schiff base in copper(II) complexes: Isolation of a zwitterionic Schiff base as the metal complex

Three copper(II) complexes [Cu(HL)2(ClO4)]ClO4·H2O (1), [Cu(L)DMF]ClO4 (2) and [CuL(NCO)][Cu2L2(NCO)2] (3) [where HL=2-[(2-Diethylamino-ethylimino)-methyl]-4-nitro-phenol, a tridentate Schiff-base] have been synthesized and characterized by elemental analysis, IR and UV–Vis spectroscopy and single-crystal X-ray diffraction studies. In complexes 2 and 3, the Schiff base is acting as a tridentate ligand. However, in complex 1, the Schiff base is present in its zwitterionic form. The denticity of the tridentate Schiff base has been modulated by the acidity of counter anions. Complexes 1 and 2 are monomeric. Copper(II) assumes square pyramidal geometry in 1 (Addison parameter (τ)=0.15) and square planar geometry in 2. The asymmetric unit of complex 3 consists of two crystallographically different double end-on cyanate bridged dimers, containing square pyramidal copper(II) {Addison parameter (τ)=0.157}. Complexes 1 and 3 crystallize in triclinic space group, P1¯ with cell dimensions a=11.3479(10), b=12.5198(9), c=13.6640(12), α=94.299(7)°, β=97.281(7)° and γ=116.007(6)° (for 1) and a=11.6149(8), b=11.8145(9), c=13.8741(13), α=65.524(6)°, β=73.373(6)° and γ=63.857(5)° (for 3), whereas complex 2 crystallizes in monoclinic space group, P21/c with cell dimensions a=7.5765(2), b=19.6005(6), c=14.5861(4) and β=102.679(1)° (for 2). The weak forces like lone pair⋯π/π⋯π/anion⋯π interactions lead to various supramolecular architectures.

Solvomorphism and catecholase activities of bis(μ-phenoxido)dicopper(II) complexes

Two phenoxido bridged dinuclear Cu(II) complexes, [Cu2(L1)2(NCO)2] (1), and [Cu2(L2)2(NCO)2]·2CH3OH (2), have been synthesized using the tridentate reduced Schiff-base ligands 2-[(2-dimethylamino-ethylamino)-methyl]-phenol (HL1) and 2-[(2-diethylamino-ethylamino)-methyl]-phenol (HL2) respectively. Re-crystallization of compound 2 from dichloromethane produced desolvated complex [Cu2(L2)2(NCO)2] (3). The compounds 2 and 3 are pseudopolymorphs or solvomorphs which differ in the crystal system (orthorhombic, Pbca for 2 and monoclinic, P21/n for 3). The complexes have been characterized by X-ray structural analyses and spectroscopic methods. In all three complexes Cu(II) is penta-coordinated having the geometry intermediate between distorted square pyramid and trigonal bipyramid with Addison parameter (τ)=0.33, 0.48 and 0.53 for 1, 2 and 3 respectively. Using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate, the catecholase activity of complexes 1 and 2 has been studied in methanol solution; compound 2 shows slightly higher catecholase activity (kcat=98.4h−1) than compound 1 (kcat=64.2h−1).

Synthesis, Crystal Structures, Magnetic Properties and Catecholase Activity of Double Phenoxido-Bridged Penta-Coordinated Dinuclear Nickel(II) Complexes Derived from Reduced Schiff-Base Ligands: Mechanistic Inference of Catecholase Activity

Three double phenoxido-bridged dinuclear nickel(II) complexes, namely [Ni(2)(L(1))(2)(NCS)(2)] (1), [Ni(2)(L(2))(2)(NCS)(2)] (2), and [Ni(2)(L(3))(2)(NCS)(2)] (3) have been synthesized using the reduced tridentate Schiff-base ligands 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL(1)), 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL(2)), and 2-[1-(3-dimethylamino-propylamino)-ethyl]-phenol (HL(3)), respectively. The coordination compounds have been characterized by X-ray structural analyses, magnetic-susceptibility measurements, and various spectroscopic methods. In all complexes, the nickel(II) ions are penta-coordinated in a square-pyramidal environment, which is severely distorted in the case of 1 (Addison parameter τ = 0.47) and 3 (τ = 0.29), while it is almost perfect for 2 (τ = 0.03). This arrangement leads to relatively strong antiferromagnetic interactions between the Ni(II) (S = 1) metal centers as mediated by double phenoxido bridges (with J values of -23.32 (1), -35.45 (2), and -34.02 (3) cm(3) K mol(-1), in the convention H = -2JS(1)S(2)). The catalytic activity of these Ni compounds has been investigated for the aerial oxidation of 3,5-di-tert-butylcatechol. Kinetic data analysis following Michaelis-Menten treatment reveals that the catecholase activity of the complexes is influenced by the flexibility of the ligand and also by the geometry around the metal ion. Electrospray ionization mass spectroscopy (ESI-MS) studies (in the positive mode) have been performed for all the coordination compounds in the presence of 3,5-DTBC to characterize potential complex-substrate intermediates. The mass-spectrometry data, corroborated by electron paramagnetic resonance (EPR) measurements, suggest that the metal centers are involved in the catecholase activity exhibited by the complexes.

Anion directed templated synthesis of mono- and di-condensed Schiff base compounds of Cu(II)

A mono-condensed Schiff base ligand has been prepared as the Cu(II) compound, [Cu2(L1)2(N3)2]·2H2O (1) (HL1=1-(N-3-methoxysalicylaldimine)-2-aminoethane), by the reaction of 1,2-diaminoethane, Cu(II) perchlorate and 3-methoxysalicyaldehyde in a 1:1:1 ratio in methanol, followed by the reaction with a large excess of NaN3. In absence of NaN3, a di-condensed compartmental ligand has been trapped as its Cu(II) compound [Cu2(L2)2⊂(H3NC2H4NH3)][{CuL2}2⊂(H3NC2H4NH3)](ClO4)4 (2) (H2L2=N,N′-ethylenebis(3-methoxysalicylaldimine). Both compounds were characterized by elemental analyses, spectral and electrochemical studies and single crystal X-ray diffraction. In compound 2, Cu(II) has a square planar coordination geometry, while in 1, Cu(II) exhibits a distorted square pyramidal geometry (Addison parameter (τ)=0.116). [CuL1(py)](ClO4) (3) is produced by following the preparation method of compound 1, but replacing NaN3 with pyridine. Formation of the compounds has been explained by an anion directed template effect.

Cis–trans isomerism in diphenoxido bridged dicopper complexes: role of crystallized water to stabilize the cis isomer, variation in magnetic properties and conversion of both into a trinuclear species

The trans-[Cu(2)L(2)Cl(2)] (1), and cis-[Cu(2)L(2)Cl(2)]·H(2)O (2) isomers of a diphenoxido bridged Cu(2)O(2) core have been synthesized using a tridentate reduced Schiff base ligand 2-[(2-dimethylamino-ethylamino)-methyl]-phenol. The geometry around Cu(II) is intermediate between square pyramid and trigonal bipyramid (Addison parameter, τ = 0.463) in 1 but nearly square pyramidal (τ = 0.049) in 2. The chloride ions are coordinated to Cu(II) and are trans oriented in 1 but cis oriented in 2. Both isomers have been optimized using density functional theory (DFT) calculations and it is found that the trans isomer is 7.2 kcal mol(-1) more favorable than the cis isomer. However, the hydrogen bonding interaction of crystallized water molecule with chloride ions compensates for the energy difference and stabilizes the cis isomer. Both complexes have been converted to a very rare phenoxido-azido bridged trinuclear species, [Cu(3)L(2)(μ(1,1)-N(3))(2)(H(2)O)(2)(ClO(4))(2)] (3) which has also been characterized structurally. All the complexes are antiferromagnetically coupled but the magnitude of the coupling constants are significantly different (J = -156.60, -652.31, and -31.54 cm(-1) for 1, 2, 3 and respectively). Density functional theory (DFT) calculations have also been performed to gain further insight into the qualitative theoretical interpretation on the overall magnetic behavior of the complexes.

New Series of Triply Bridged Dinuclear Cu(II) Compounds: Synthesis, Crystal Structure, Magnetic Properties, and Theoretical Study

Five new triply bridged dinuclear Cu(II) compounds have been synthesized, and their magnetic properties have been measured and characterized. The magnetic coupling constants (J) of these compounds plus a previously structurally characterized compound of the same type have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. Two of the compounds are ferromagnetically coupled, and three are antiferromagnetically coupled with J values in the [+150, -40] cm(-1) range. The validity of the structural aggregate Addison's parameter as a qualitative magneto-structural correlation is confirmed. The origin of the magnetic interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory-based calculations using a variety of state of the art exchange-correlation potentials. It is shown that the long-range separated LC-ωPBE provides the overall best agreement with experiment for this family as well as for a set of previously reported hetero triply bridged dinuclear Cu(II) compounds, especially for ferromagnetic systems.

Effect of anionic co-ligands on structure and magnetic coupling of bis(μ-phenoxo)-bridged dinuclear copper(II) complexes

Two phenoxo bridged dinuclear Cu(II) complexes, [Cu2L2(NO2)2] (1) and [Cu2L2(NO3)2] (2) have been synthesized using the tridentate reduced Schiff-base ligand 2-[(2-dimethylamino-ethylamino)-methyl]-phenol (HL). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The structures of the two compounds are very similar having the same tridentate chelating ligand (L) and mono-dentate anionic ligand nitrite for 1 and nitrate for 2. In both complexes Cu(II) is penta-coordinated but the square pyramidal geometry of the copper ions is severely distorted (Addison parameter (τ)=0.33) in 1 while the distortion is quite small (average τ=0.11) in 2. These differences have marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J=−140.8 and −614.7cm−1 for 1 and 2, respectively) show that the coupling is much stronger in 2.

Structural, electrochemical and spectroscopic characterization of a new [Cu 2L 2(μ-Cl) 2] 2[CuCl 4] 2 dimer complex

The bis{(μ 2-chloro)[2-(imidazol-4-yl)ethyl][(1-methylimidazol-2-yl)methyl]amine}dicopper(II) bis[tetrachloro-cuprate (II)] complex [Cu 2(HISMIMA) 2Cl 2] 2(CuCl 4) 2 (HISMIMA:[(2-(imidazol-4-yl)ethyl)(1-methylimidazol-2-yl)methyl)amine]) was obtained by serendipity during the reaction of the mononuclear [Cu(HISMIMA)Cl 2] complex and gaseous nitric oxide in methanolic solution. The title complex unit cell has the composition: an anion complex {[Cu 2(HISMIMA) 2Cl 2][CuCl 4] 2} 2− ( 1) and a cation complex [Cu 2(HISMIMA) 2Cl 2] 2+ ( 2). Cation 2 displays a crystallographic centrosymmetric Cu 2Cl 2 core with each Cu II atom coordinated to the tripodal ligand in a square pyramidal geometry (Addison parameter τ=0.07). In 1, a distorted octahedral geometry is observed, in which the Cu II ions are coordinated in a way similar to that in 2 but with an additional interaction with the [CuCl 4] 2− ions. Cyclic voltammetric experiments reveal that the title complex does not dissociate in acetonitrile solution and has E 1/2=−0.24 V vs NHE (Δ E p=0.19 V, i pa/ i pc=0.75) for the Cu IICu II to Cu ICu I process at the Cu(μ-Cl) 2Cu core.

Three new dinuclear copper(ii) complexes with [Cu(μ1,3-N3)2Cu]2+and [Cu(μ1,1-N3)2Cu]2+asymmetrical cores: syntheses, structures and magnetic behaviour

Three new dinuclear copper(II) complexes, derived from end-to-end and end-on azido bridging ligands and triamine derivatives, have been synthesized and their crystal structures have been determined by X-ray diffraction methods. These are the dinuclear end-to-end compounds, [Cu2(μ1,3-N3)2(Et3dien)2](ClO4)2 (1) and [Cu2(μ1,3-N3)2(Medpt)2](ClO4)2 (2), and the dinuclear end-on compound [Cu2(μ1,1-N3)2(Medien)2](ClO4)2 (3) (Et3dien is triethyldiethylenetriamine, Medpt is methyldipropylenetriamine and Medien is methyldiethylenetriamine). The [Cu(μ-N3)2Cu]2+ cores are asymmetrical in all 3 compounds. Variable temperature magnetic susceptibility data were collected and fitted to the appropriate equation derived from the Hamiltonian H = −JS1S2. 1 shows unusual ferromagnetic interactions with J = 9 cm−1 through the end-to-end azido bridges while 2 shows an antiferromagnetic interaction through the end-to-end azido bridges with the highest reported absolute magnitude of J = −105 cm−1. The magnetic data of 1 and 2 have been correlated with the Addison parameter, τ, and mainly with the Cu–N3–Cu torsion angle, Δ. 3 shows an unusual antiferromagnetic interaction with J = −16.8 cm−1 through the end-on azido bridges.