Chair Ring Research Articles

Understanding the microstructure evolution of Fe-induced diamond with DFT study: Etching and graphitization

Studying diamond graphitization is a crucial issue in ultra-precision machining because it sheds light on the reason for material removal during polishing. The polishing disc made of cast iron is usually used to process diamonds, and a high-quality surface can be obtained. However, the graphitization mechanism induced by iron (Fe) is still obscure. This paper employs the density-functional theory (DFT) method to elucidate the mechanism by which Fe induces diamond graphitization. The results demonstrated that Fe atoms at the metastable adsorption sites (P3) on the surface could change some C–C interactions between layers. Notably, multiple Fe atoms at the P3 sites could alter the region of surface graphitization and the structural dissociation direction. The surface area close to Fe atoms became stable, while the surrounding surface areas were susceptible to oblique dissociation into graphite-like structures. Moreover, we speculated that the material removal rate was related to the moving activation energy of Fe atoms. Based on the charge-transfer and microstructural evolution, the phenomenon of Fe-atom-induced diamond graphitization was attributed to varying the connections between sixfold chair rings and promoting their weakening and dissociation rather than breaking the structure of sixfold chair rings.

DFT insight of hydroxide degradation pathways for heterocyclic quaternary ammonium cations in anion exchange membranes

The alkaline stability of the heterocyclic quaternary ammoniums (QAs) is crucial for the long-term operation of anion exchange membrane fuel cells (AEMFCs). Here, we calculate the degradation barriers of 21 heterocyclic QAs and analyze the degradation mechanism systematically by density functional theory (DFT). We have found that the chair conformation and ring structure of heterocyclic QAs can inhibit Hoffman degradation of β-hydrogens and that methyl SN2 is the primary degradation pathway for most heterocyclic QAs. Higher ring strain and the introduction of electron-withdrawing groups are disadvantageous to the stability. The positions of substituted methyl affect the stability of the molecules significantly. Forming bicyclic structures is also an effective strategy to improve stability. Among tethering strategies of anion exchange membranes (AEMs), tethering at the 4-position is more stable than at the 1-position. The superacid-catalyzed condensation reaction is still the best AEM preparation strategy which balances the stability and synthetic difficulty. Compared with the experimental value, the average error of simulation is only 0.56 kcal mol−1. Our prediction method can also be extended to various alkali concentrations, and the results are consistent with the experiments. At low alkali concentrations, the heterocyclic QAs mainly degrade by SN2 reactions. At high alkali concentrations, the groups mainly degrade by Hofmann elimination reactions.

First-principles study of the microstructure evolution of the diamond (110) surface with the adsorption of Fe atoms

Understanding the diamond graphitization mechanism is an essential subject in manufacturing research since it helps elucidate the reason for the material removal. Our work addressed the mechanism of Fe-induced graphitization of diamond (110) surfaces (Dia-(110)-Surf) by first-principles calculations. The results pointed out that Fe atoms adsorbed at hollow sites could acquire the most stable configuration on the Dia-(110)-Surf. Meanwhile, the Fe adatom could change interlayer binding energies of CC bonds of various layered. As the amount of Fe atoms increased, the weakening/enhancement effect of CC bonds tended to be apparent. Interestingly, Fe adatoms not only changed interlayer binding energies of CC nearby but also affected the dissociation direction of the surface microstructure. The weakened CC bonds could provoke the flattening of the sixfold chair ring structure of C atoms. The extension direction of the sixfold chair ring structure changed from horizontal to oblique, resulting in eliminating lateral compressive stress. It might be the origin of the Fe-induced graphitization of Dia-(110)- Surf. Moreover, the migration behaviors of the Fe atom have been studied. It could be inferred that the migration activation energy and movement direction of Fe adatoms were associated with the material removal rate.

Conformational diversity of 1‑chloro-1-chloromethylsilacyclohexane with experimental (Raman and IR) and computational (DFT, MP2) methods

1‑chloro-1-chloromethylsilacyclohexane (1-Cl-1-ClMSiCH) is a newly synthesized molecular compound whose conformational analysis was performed by means of vibrational spectroscopy and theoretical calculations. Conventional ATR-FTIR and Raman spectroscopic methods were used to obtain vibrational spectra of the liquid sample. Additionally, FTIR spectra of the compound isolated in low-temperature neon and nitrogen matrices were registered to make a complete assignment of the experimental vibrational spectral bands. All theoretically possible 38 canonical ring conformations considering axial/equatorial and cis/trans/gauche-/gauche + positions of the Cl and CH2Cl group were analyzed by utilizing MP2 and B3LYP at aug-cc-pVTZ theory level. The most stable local energy minima were investigated in detail, with the global energy minimum structure being in the chair axial trans conformation. Detailed analysis of the potential energy surface revealed the transition states (TS) and the energy barriers. The conformational path was found to be the chair→ envelope/half-chair (TS)→ skew-boat C1→ boat (TS)→ skew-boat C2. The energy barrier for 1C4 to 1S3 conversion was found to be 4.94 kcal/mol while for the reverse process–it was calculated to be 0.26 kcal/mol. The vibrational analysis and the experimental spectra suggest that the four lowest energy (chair ring) conformers coexist at room temperature. The energy barrier for gauche to trans conversion is 1.15 kcal/mol for axial and 1.04 kcal/mol for equatorial conformers, and it is possible to observe these processes in low-temperature matrices.

Crystal structure of trans-di-chlorido-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N)chromium(III) bis-(form-amide-κO)(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N)chromium(III) bis-[tetra-chlorido-zincate(II)

The structure of the title compound, [CrCl2(C10H24N4)][Cr(HCONH2)2(C10H24N4)][ZnCl4]2 (C10H24N4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, cyclam; HCONH2 = formamide, fa), has been determined from synchrotron X-ray data. The asymmetric unit contains two independent halves of the [CrCl2(cyclam)]+ and [Cr(fa)(cyclam)]3+ cations, and one tetra-chlorido-zincate anion. In each complex cation, the CrIII ion is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and two Cl ligands or two O-bonded formamide mol-ecules in a trans axial arrangement, displaying a distorted octa-hedral geometry with crystallographic inversion symmetry. The Cr-N(cyclam) bond lengths are in the range 2.061 (2) to 2.074 (2) Å, while the Cr-Cl and Cr-O(fa) bond distances are 2.3194 (7) and 1.9953 (19) Å, respectively. The macrocyclic cyclam moieties adopt the centrosymmetric trans-III conformation with six- and five-membered chelate rings in chair and gauche conformations. The crystal structure is stabilized by inter-molecular hydrogen bonds involving the NH or CH groups of cyclam and the NH2 group of coordinated formamide as donors, and Cl atoms of the ZnCl4 2- anion as acceptors.

Trajectory-Based Simulation of EPR Spectra: Models of Rotational Motion for Spin Labels on Proteins.

Direct time-domain simulation of continuous-wave (CW) electron paramagnetic resonance (EPR) spectra from molecular dynamics (MD) trajectories has become increasingly popular, especially for proteins labeled with nitroxide spin labels. Due to the time-consuming nature of simulating adequately long MD trajectories, two approximate methods have been developed to reduce the MD-trajectory length required for modeling EPR spectra: hindered Brownian diffusion (HBD) and hidden Markov models (HMMs). Here, we assess the accuracy of these two approximate methods relative to direct simulations from MD trajectories for three spin-labeled protein systems (a simple helical peptide, a soluble protein, and a membrane protein) and two nitroxide spin labels with differing mobilities (R1 and 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC)). We find that the HMMs generally outperform HBD. Although R1 dynamics partially resembles hindered Brownian diffusion, HMMs accommodate the multiple dynamic time scales for the transitions between rotameric states of R1 that cannot be captured accurately by a HBD model. The MD trajectories of the TOAC-labeled proteins show that its dynamics closely resembles slow multisite exchange between twist-boat and chair ring puckering states. This motion is modeled well by HMM but not by HBD. All MD-trajectory data processing, stochastic trajectory simulations, and CW EPR spectral simulations are implemented in EasySpin, a free software package for MATLAB.

Increase in local crystalline order across the limit of stability leads to cubic-hexagonal stacking in supercooled monatomic (mW) water.

At the limit of stability of a supercooled tetrahedral liquid modeled by monatomic (mW) water potential, it was recently shown that relaxation occurs across a unique value of per particle potential energy (ϕmid ), which corresponds to a dynamical (non-stationary) condition of Gibbs free energy function G(T, P, N, ϕ): [∂2(G/N)/∂ϕ2 = 0] and [∂(G/N)/∂ϕ ≠ 0]. In this work, we explore the inherent structures responsible for the formation of the amorphous states through such a mechanism of relaxation of mW liquid. We first identify 6-member boat and chair shaped rings using a criterion based on the internal dihedral angles. We then consider the stacking of the cubic diamond (10-atom cluster with 4 chair shaped rings) and hexagonal wurtzite (12-atom cluster with 3 boat and 2 chair shaped rings) units through a shared chair ring. We find that the local crystalline (tetrahedral) order is exhibited by the eclipsed bond particles of the laterally connected wurtzite units which are stacked from both sides with the diamond units (DWD stacking). Increasingly longer range crystalline order is obtained as the number of stacked wurtzite layers increases: the particles shared by the stacked (laterally connected) wurtzite layers in DWWD show a longer range crystalline order. An even longer range crystalline order is exhibited by the eclipsed bond particles of the middle (laterally connected) wurtzite layer of DWWWD stacking. We find that cubic-hexagonal stacking occurs primarily in the form of DWD layers across the limit of stability. The local tetrahedral order of the purely cubic (diamond) network particles (which are not shared with wurtzite units) deviates significantly from that of the hexagonal crystal. Nonetheless, the average length of the bonds in the purely cubic network approaches that in the hexagonal crystal very closely. Thus a large increase in the purely cubic ice across the instability also leads to an increase in the local crystalline order in the form of bond-lengths. Our results are consistent with previous experimental and simulation studies which find a significant fraction of cubic ice along with cubic-hexagonal stacking layers in deeply supercooled water.

Crystal structure of trans-diammine(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ(4) N)chromium(III) tetra-chlorido-zincate chloride monohydrate from synchrotron data.

The asymmetric unit of the title complex salt, [Cr(C10H24N4)(NH3)2][ZnCl4]Cl·H2O, is comprised of four halves of the Cr(III) complex cations (the counterparts being generated by application of inversion symmetry), two tetra-chlorido-zincate anions, two chloride anions and two water mol-ecules. Each Cr(III) ion is coordinated by the four N atoms of the cyclam (1,4,8,11-tetra-aza-cyclo-tetra-deca-ne) ligand in the equatorial plane and by two N atoms of ammine ligands in axial positions, displaying an overall distorted octa-hedral coordination environment. The Cr-N(cyclam) bond lengths range from 2.0501 (15) to 2.0615 (15) Å, while the Cr-(NH3) bond lengths range from 2.0976 (13) to 2.1062 (13) Å. The macrocyclic cyclam moieties adopt the trans-III conformation with six- and five-membered chelate rings in chair and gauche conformations. The [ZnCl4](2-) anions have a slightly distorted tetra-hedral shape. In the crystal, the Cl(-) anions link the complex cations, as well as the solvent water mol-ecules, through N-H⋯Cl and O-H⋯Cl hydrogen-bonding inter-actions. The supra-molecular set-up also includes N-H⋯Cl, C-H⋯Cl, N-H⋯O and O-H⋯Cl hydrogen bonding between N-H or C-H groups of cyclam, ammine N-H and water O-H donor groups, and O atoms of the water mol-ecules, Cl(-) anions or Cl atoms of the [ZnCl4](2-) anions as acceptors, leading to a three-dimensional network structure.

Crystal structure of bis-[trans-(1,4,8,11-tetra-aza-cyclo-tetra-decane-κ(4) N)bis-(thio-cyanato-κN)chromium(III)] tetra-chlorido-zincate from synchrotron data.

The structure of the title compound, [Cr(NCS)2(cyclam)]2[ZnCl4] (cyclam = 1,4,8,11-tetra-aza-cyclo-tetra-decane, C10H24N4), has been determined from synchrotron data. The asymmetric unit contains two independent halves of the Cr(III) complex cations and half of a tetra-chlorido-zincate anion. In each complex cation, the Cr(III) atom is coordinated by the four N atoms of the cyclam ligand in the equatorial plane and by two N-bound NCS(-) anions in a trans axial arrangement, displaying a distorted octa-hedral geometry with crystallographic inversion symmetry. The mean Cr-N(cyclam) and Cr-N(NCS) bond lengths are 2.065 (4) and 1.995 (6) Å, respectively. The macrocyclic cyclam moieties adopt centrosymmetric trans-III configurations with six- and five-membered chelate rings in chair and gauche configurations, respectively. The [ZnCl4](2-) anion, which lies about a twofold rotation axis, has a slightly distorted tetra-hedral geometry. The crystal packing is stabilized by hydrogen-bonding inter-actions between the N-H groups of the cyclam ligands, the S atoms of the NCS(-) groups and the Cl(-) ligands of the anion.

Synthesis, structural and conformational study of some esters derived from 3-methyl-3-azabicyclo[3.2.1]octan-8(α and β)-ols

A series of α and β-esters bearing a 3-methyl-3-azabicyclo[3.2.1]octane moiety as well as methyl and aryl substituents were synthesized and studied by 1H and 13C NMR spectroscopies. In CDCl3 solution, at room temperature, a chair-envelope conformation for the bicycle moiety with the N-CH3 group in equatorial position with respect to the chair ring is proposed for both, α and β-esters. The chair conformation of the piperidine ring is puckered at C8 in the α-epimers and it is flattened at N3, in the β-epimers. Free rotation of the acyloxy group around the C8O bond has also been deduced. Analgesic activity of four of these substances was studied. 8β-Benzoyloxy-3-methyl-3-azabicyclo[3.2.1]octane demonstrated significant analgesic activity in the hot plate test compared to morphine. By measuring the rectal temperature in mice, results also showed a significant antipyretic activity of this compound.

6α,7α-Epoxy-5α-hydroxy-1-oxo-22R-witha-2,24-dienolide(withanolide B), 5β,6β-Epoxy-4β,20-dihydroxy-1-oxo-22R-witha-2,24-dienolide(withanolide D), and 4β,27-Dihydroxy-1-oxo-22R-witha-2,5,24-trienolide(5,6-deoxywithaferin A) in Roots of Withania somnifera: Isolation and Their Crystal Structures

6α,7α-Epoxy-5α-hydroxy-1-oxo-22R-witha-2,24-dienolide (C28H38O5), 5β,6β-epoxy-4β,20-dihydroxy-1-oxo-22R-witha-2,24-dienolide (C28H38O6), and 4β,27-dihydroxy-1-oxo-22R-witha-2,5,24-trienolide (C28H38O5), were isolated from Withania somnifera roots. The structures of these withanolides were established by spectroscopic analysis and X-ray diffraction studies as withanolide B, withanolide D, and 5,6-deoxywithaferin A, respectively. All three compounds crystallize in the orthorhombic space group P212121 with unit cell parameters: a = 9.1012(3) A, b = 12.2728(4) A, c = 21.5396(7) A, Z = 4 for withanolide B; a = 7.6569(5) A, b = 9.9426(7) A, c = 33.767(2) A, Z = 4 for withanolide D; and a = 6.9310(3) A, b = 10.6745 (4) A, c = 34.667(2) A, Z = 4 for 5,6-deoxywithaferin A, respectively. The crystal structures have been solved by direct methods and refined to R 1 = 0.024 for 4,290 unique reflections (withanolide B), R 1 = 0.042 for 4,601 unique reflections (withanolide D), and R 1 = 0.033 for 4,626 unique reflections (5,6-deoxywithaferin A), respectively. Rings B, C, D of the steroid skeletons are trans connected while ring C adopts a chair conformation, five-membered ring D adopts a half-chair, and the δ-lactone ring E in the side chain adopts a sofa conformation. For withanolide B, rings A and B are trans connected and both rings A and B exist in a half-chair conformation; for withanolide D, rings A and B are cis connected, and ring A has a sofa conformation while ring B has a distorted boat conformation; for 5,6-deoxywithaferin A, ring A has a half chair conformation and ring B exists as a boat conformation. The crystal structures of 6α,7α-epoxy-5α-hydroxy-1-oxo-22R-witha-2,24-dienolide (withanolide B), 5β,6β-epoxy-4β,20-dihydroxy-1-oxo-22R-witha-2,24-dienolide (withanolide D), and 4β,27-dihydroxy-1-oxo-22R-witha-2,5,24-trienolide (5,6-deoxywithaferin A) are described.

Conformational studies of gas-phase ribose and 2-deoxyribose by density functional, second order PT and multi-level method calculations: the pyranoses, furanoses, and open-chain structures

We present an extensive computational study of a complex conformational isomerism of two gas phase pentoses of biological and potential astrobiological importance, d-ribose and 2-deoxy-d-ribose. Both cyclic (α- and β-pyranoses, α- and β-furanoses) and open-chain isomers have been probed using second order Møller–Plesset perturbation theory (MP2), M06-2X density functional, and multi-level G4 methods. This study revealed a multitude of existing minima structures. Numerous furanose conformers found are described with the Altona and Sundaralingam pseudorotation parameters. In agreement with the recent gas-phase microwave (MW) investigation of Cocinero et al., the calculated free ribose isomers of lowest energy are the two β-pyranoses with the 1C4 and 4C1 ring chair conformations. Both β-pyranoses lie within 0.9kJ/mol in terms of ΔG(298K) (G4), thus challenge the computational methods used to predict the ribose global minimum. The calculated most favoured ribofuranose is the α-anomer having the twist 2T1 ring conformation, put 10.4kJ/mol higher in ΔG than the global minimum. By contrast with d-ribose, the lowest energy 2-deoxy-d-ribose is the α-pyranose, with the most stable 2-deoxy-d-furanose (the α-anomer) being only 6.2kJ/mol higher in free energy. For both pentoses, the most favoured open-chain isomers are significantly higher in energy than the low-lying cyclic forms. A good overall agreement is observed between the M06-2X and MP2 results in terms of both the existing low-energy minima structures and intramolecular H-bonding geometrical parameters. The natural orbital analysis confirms the occuring of the endo- and exo-anomeric effects and maximization of intramolecular H-bonding in the lowest-lying pyranoses and furanoses of both sugars.

N,N-Dimethyldehydroabietylammonium chloride ethanol monosolvate

The title compound {systematic name: 1-[(1R,4aS,10aR)-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octa­hydro­phenan­thren-1-yl]-N,N-di­methyl­methanaminium chloride ethanol monosolvate}, C22H36N+·Cl−·C2H6O, was synthesized from dehydroabietylamine by N-methyl­ation with formaldehyde/formic acid and transformation into the hydro­chloride. The de­hydro­abietyl moiety exhibits the usual conformation with the two cyclo­hexane rings in chair and half-chair conformations and a trans-ring junction. The crystal structure is built up from columns of the de­hydro­abietyl moieties stacked along the a axis. These columns are held together by the chloride ions via N—H⋯Cl and C—H⋯Cl inter­actions, which establish a two-dimensional network parallel to (010). The ethanol solvent mol­ecules are located between the columns and anchored via O—H⋯Cl hydrogen bonds.

The Interaction of Sorbitol with Caffeine in Aqueous Solution

Molecular dynamics simulations were carried out on a system of caffeine interacting with the sugar alcohol sorbitol. The system examined had a caffeine concentration 0.083 m and a sugar concentration 1.08 m. The trajectories of all molecules in the system were collected over a period of 80 ns and analyzed to determine whether there is any tendency for sorbitol to bind to caffeine, and if so, by what mechanism. The results show that the sorbitol molecules have an affinity for the caffeine molecules and that the binding occurred by the interaction of the aliphatic hydrophobic protons of the sugar with the caffeine face. This intermolecular association via face-to-face stacking, as suggested by simulation studies, is similar to that found for sucrose and for D-glucose, which overwhelmingly exists in the pyranose ring chair form in aqueous solution, as well as for caffeine-caffeine association. The sorbitol molecules, however, exist as relatively extended chains and are, therefore, topologically quite different from the sugars sucrose and glucose. The comparison of the average conformation of sorbitol molecules bound to caffeine with that of molecules in the free state shows a substantial similarity.

Cholest-5-en-3β-yl 3-(4-ethoxyphenyl)prop-2-enoate

In the asymmetric unit of the title compound, C38H56O3, there are two symmetry-independent mol­ecules that differ in the rotation angle along the C—O bond between the 3-(4-eth­oxy­phen­yl)prop-2-enoate and cholest-5-en-3β-yl groups by 169.3 (3)°. In both mol­ecules, steroid ring B adopts a half-chair conformation, rings A and C adopt a chair conformation and ring D exists in an envelope form. The two symmetry-independent mol­ecules pack in the crystal into separate layers parallel to (-102) with their long axis parallel to the [201] direction. Short inter­molecular C—H⋯O and C—H⋯π contacts are observed.

(3R,4S,5S,8S,10R,13R)-3-Hydroxykaura-9(11),16-dien-18-oic acid

The title compound, C20H28O3, was isolated during our investigation into the chemical composition and pharmacological activity of Centipeda cunninghamii (DC.) A. Braun & Asch. (Asteraceae). The enanti­opure compound, a diterpene with a carbon skeleton, is composed of three six- and one five-membered rings in chair, twist-boat, half-chair and envelope conformations, respectively. Each mol­ecule makes one intra- and one inter­molecular O—H⋯O hydrogen bond in the crystal lattice, forming hydrogen-bonded chains along [010]. The absolute configuration of the compound was assigned on the basis of optical rotation measurements.

Combined experimental powder X-ray diffraction and DFT data to obtain the lowest energy molecular conformation of friedelin

Friedelin molecular conformers were obtained by Density Functional Theory (DFT) and by ab initio structure determination from powder X-ray diffraction. Their conformers with the five rings in chair-chair-chair-boat-boat, and with all rings in chair, are energy degenerated in gas-phase according to DFT results. The powder diffraction data reveals that rings A, B and C of friedelin are in chair, and rings D and E in boat-boat, conformation. The high correlation values among powder diffraction data, DFT and reported single-crystal data indicate that the use of conventional X-ray diffractometer can be applied in routine laboratory analysis in the absence of a single-crystal diffractometer.

Fourteen membered hexaaza copper macrocycle: Synthesis, characterization, crystal structures and the consequence of anion coordination

Fourteen membered hexaaza macrocyclic complexes of the type [CuLX2] (where L = 3,10-bis(benzyl)1,3,5,8,10,12-hexaazacyclotetradecane and X=ClO4-, SCN−) and [CuL(CH3CN)2](PF6)2(CH3CN)2 have been synthesized by template assisted condensation reaction. They have been characterized by spectral and X-ray crystallographic techniques. It was of interest to investigate the effect of anions on the gross geometry and chemical properties of Cu(II) ion. The crystal structure of all the complexes show axially elongated octahedral geometry with weakly coordinated anions. The macrocyclic ring adopts the trans-III configuration with six- and five-membered chelate rings in chair and gauche conformation, respectively. The IR and other spectral properties are consistent with the result of X-ray diffraction. It was observed that in the solid state the arrangement of the coordination sphere is distorted octahedral whereas in solution, a square-planar structure is predominant. The molar conductivity of the complexes indicates that the axially bonded anions are almost entirely dissociated in acetonitrile solution. The EPR spectra of complexes 1–3 are axial and consistent with a dx2-y2 ground state.

Synthesis, Crystal Structure and Spectroscopic Properties of (Acetylacetonato)(1,4,8,11‐tetraazacyclotetradecane)chromium(III) Diperchlorate

AbstractThe complex [Cr(cyclam)(acac)](ClO4)2·0.5H2O (cyclam = 1,4,8,11‐tetraazacyclotetradecane; acac = acetylacetonate) was prepared and structurally characterized by single‐crystal X‐ray diffraction at 100 K. The chromium atom is in a slightly distorted octahedral environment with four nitrogen atoms of the macrocyclic ligand and two O‐bonded acac molecules in cis position. The cyclam ligand adopts the folded cis‐V configuration with six‐ and five‐membered chelate rings in chair and gauche conformation, respectively. The average Cr–N(cyclam) and Cr–O(acac) bonds are 2.080(4) and 1.941(3) Å, respectively. The IR and visible spectral properties are also described.

The synthesis, crystal structures and antimicrobial studies of C‐methyl‐substituted hexaaza macrocycle of Cu(II) having aromatic pendant arm

AbstractCu(II) complexes of 14‐membered hexaaza macrocyclic ligand with C‐methyl substituent of the type [CuL](X)2 (where L = 3,10‐bisbenzyl‐6,13‐dimethyl‐1,3,5,8,10,12‐hexaazacyclotetradecane, and X = ClO4−, PF6−) were synthesized by tandem reaction. They were characterized by spectral and single‐crystal X‐ray diffraction techniques. The complexes show distorted octahedral geometry and the counter ions are weakly coordinated to the metal ion at the axial positions. The macrocyclic ring adopts the trans‐III configuration with six‐ and five‐membered chelate rings in chair and gauche conformation, respectively. It was observed that in the solid state the arrangement of the coordination sphere is distorted octahedral whereas, in solution, a square‐planar structure is predominant. The molar conductance of the complexes indicates that the axially bonded anions are almost dissociated in acetonitrile solution. The Electron Paramagnetic Resonance (EPR) spectrum of complex 1 is axial and consistent with a dx2 − y2 ground state. The [CuL](ClO4)2 was found to be active against the tested microorganism. Copyright © 2011 John Wiley & Sons, Ltd.