Phase diagrams and physical properties of binary ferroelectric mixtures based on a series of chiral α-cyanocinnamate derivatives

We report a detailed investigation of binary mixtures composed of members of the homologous series of (S)-4′-(2-n-alkoxypropanoyloxy)biphenyl-4-yl 4-n-alkoxy- f-cyanocinnamates. The phase transition curves for these mixtures have no minima. On the contrary, eutectic behaviour was obtained if the members of this homologous series were mixed with structurally different chiral cinnamic acid derivatives and other ferroelectric liquid crystal materials. Spontaneous polarization, tilt angle and dielectric constant results were obtained for three of the single compounds and nine ferroelectric mixtures.     

Synthesis,structure, and properties of the complex [Cu(L)Cl] ∙ 2H<Subscript>2</Subscript>O

The crystal structure of copper(II) complex with the HL ligand obtained from 3-[4-carboxyphenylazo] penta-2,4-dione and ethylenediamine (En) was determined by X-ray diffraction. The crystals are orthorhombic: a = 7.329(3), b = 15.393(5), c = 18.474(7) Å, V = 2084.1(12) ų, space group P2₁2₁2₁, Z = 4, ρ_(calcd.) = 1.486 g/cm³, R = 0.0441. The copper atom is coordinated by four nitrogen atoms of two En ligands and by the chlorine atom in an axial position according to the extended square pyramid geometry (4 + 1) (CIF file CCDC no. 1436882).     

Syntheses,crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2′-bipyridine and TCNQ

From the aqueous-methanolic systems Ni(NO₃)₂ – LiTCNQ – 5,5′-dmbpy and Ni(NO₃)₂ – LiTCNQ – 4,4′-dmbpy three novel complexes [Ni(5,5′-dmbpy)₃](TCNQ)₂ (1), [Ni(4,4′-dmbpy)₃](TCNQ)₂ (2) and [Ni(4,4′-dmbpy)₃]₂(TCNQ-TCNQ)(TCNQ)₂∙0.60H₂O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5′-dmbpy)]²⁺ (1) or [Ni(4,4′-dmbpy)]²⁺ (2 and 3). The anionic parts of the respective crystal structures 1–3 are formed by TCNQ^⋅- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)^2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2–300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQ^⋅- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)^2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQ^⋅- anion-radicals.     

How dependent are molecular and atomic properties on the electronic structure method? Comparison of Hartree‐Fock,DFT, and MP2 on a biologically relevant set of molecules

This article compares molecular properties and atomic properties defined by the quantum theory of atoms in molecules (QTAIM) obtained from three underlying levels of theory: MP2(full), density functional theory (DFT) (B3LYP), and Hartree‐Fock (H‐F). The same basis set (6‐311++G(d,p)) has been used throughout the study. The calculations and comparisons were applied to a set of 30 small molecules representing common fragments of biological molecules. The molecular properties investigated are the energies and the electrostatic moments (up to and including the quadrupoles), and the atomic properties include electron populations (and atomic charge), atomic dipolar and quadrupolar polarizations, atomic volumes, and corrected and raw atomic energies. The Cartesian distance between dipole vectors and the Frobenius distance between the quadrupole tensors calculated at the three levels of theory provide a measure of their correlation (or lack thereof). With the exception of energies (atomic and molecular), it is found that both DFT and H‐F are in excellent agreement with MP2, especially with regards to the electrostatic mutipoles up to the quadrupoles, but DFT and MP2 agree better in almost all studied properties (with the exception of molecular geometries). QTAIM properties whether obtained from H‐F, DFT(B3LYP), or MP2 calculations when used in the construction of empirical correlations with experiment such as quantitative structure‐activity‐(or property)‐relationships (QSAR/QSPR) are equivalent (because the properties calculated at the three levels are very highly correlated among themselves with r² typically >0.95, and therefore preserving trends). These results suggest that the massive volume of results that were published in the older literature at the H‐F level is valid especially when used to study trends or in QSAR or QSPR studies, and, as long as our test set of molecules is representative, there is no pressing need to re‐evaluate them at other levels of theory except when inadequate basis sets were used by today's standards. Extensive tabulation of molecular and atomic properties at the three theoretical levels is available in the Supporting Information, including optimized geometries, molecular energies, virial ratios, molecular electrostatic moments up to and including hexadecapoles, atomic populations, atomic volumes, atomic electrostatic moments up to and including the quadrupoles, and atomic energies. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Jørgensen complex within a molecular container: selective encapsulation of trans-[Co(en)2Cl2]+ into cucurbit[8]uril and influence of inclusion on guest's properties

The unprecedented selective encapsulation of trans-[Co(en)2Cl2]+ from the mixture of trans and cis isomers into the cavity of macrocyclic cavitand cucurbit[8]uril (C48H48N32O16, CB[8]) leads to the inclusion compound {trans-[Co(en)2Cl2]@CB[8]}Cl.17H2O (1). Single-crystal X-ray analysis, 1H NMR, and ESI-MS spectra confirm the formation of host-guest complex 1 in both solid state and solution. The geometry of the complex cation alters significantly upon inclusion, which causes appreciable hypsochromic shifts of the absorption bands of the guest complex. According to TGA data, inclusion of trans-[Co(en)2Cl2]+ dramatically stabilizes the complex toward thermal decomposition. Encapsulation of trans-[Co(en)2Cl2]+ into the CB[8] cavity also increases the stability of the metal complex toward isomerization into the cis form. The supramolecular adduct {cis-[Co(en)2(H2O)2](CB[8])6}Cl3.ca109.5H2O (2) was isolated only after prolonged heating of an aqueous solution of 1 at 120 degrees C in an evacuated tube; it was characterized by X-ray crystallography, IR, and elemental analysis.     

Erratum to“Single-crystal structure of two-dimensional organic framework based on donor-acceptor interactions with chargetransfer effect”[Sci.China Chem.,2021,64:1510–1514]

Erratum to:Sci China Chem,2021,64:1510-1514,doi:10.1007/s11426-021-1030-7 Due to the error during the production process,the Figure 3 was missing in the above referenced publication[1].The corrected Figure 3 is as follows.The online version of the original article can be found at doi:10.1007/s11426-021-1030-7.     

Synthesis,crystal structure and magnetic properties of the first dinuclear copper(II)–iron(II) complex [Cu(L)Fe(CN)5NO] based on nitroprusside

The nitrosyl cyanide [Cu(L)Fe(CN)₅NO] was prepared by the reaction of [Cu(L)]Cl₂ [L = 3, 10-bis(2-hydroxymethyl)-1,3,5,8,10,12-hexaazacyclotetradecane] with Na₂[Fe(CN)₅NO]·2H₂O in aqueous solution. Single-crystal analysis revealed that the title complex is the first structurally characterized dinuclear copper(II)–iron(II) complex based on the nitroprusside. Variable temperature magnetic susceptibility measurements (4.0–180.0 K) show the occurrence of very weak antiferromagnetic interactions between the copper(II) ions with zJ = –0.410 cm^–1.