Computer Design of Fe-M-Fe (M = Co,Ni, Cu,Zn) Complexes with Bis-Salicylaldiminate Linker Functionalized with 1,10-Phenanthroline

Russian Journal of General Chemistry - Density functional theory method UB3LYP*/6-311++G(d,p) has been applied to the study of geometry, energy, and magnetic characteristics of the isomers of...     

Photo- and thermochromic spirans. 16. 2-Oxo-3-phenyl-5,5-dimethylspiro(1,3-oxazolidine-4,2′-[2h]chromenes)

New spirans of the 5,5-dimethyl-3-phenyl-2-oxazolidone series that display photo-chromic properties in alcohol solutions at -80 °C were synthesized. The photoinduced forms are characterized by the presence of two long-wave absorption bands at 350–420 nm and 500–650 nm. The ¹H and ¹³C NMR spectra were studied. Anisochronicity of the diastereotopic methyl groups of the oxazolidone ring shows up only in the ¹³C NMR spectra.See [1] for communication 15.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1035, August, 1985.     

Inversion of tetrahedral configuration of bis-{4-aminomethylenepyrazole-5-thion(seleno)ato} nickel(II) complexes

Novel bis-chelate Ni(II) complexes with a series of 1,3-disubstituted 4-aminomethylenepyrazole-5-thion(seleno) derivatives have been prepared. An inversion of the tetrahedral configuration at the metal centre in these complexes proceeds in solution via the intramolecular diagonal twist rearrangement on the NMR time scale which was followed by coalescence studies on several pairs of diastereotopic protons. The activation barriers are: ΔG²(T_c) = 41–74 kJ mol^?1, _c = 218–373 K. The bulky substituents R₃ at the aldimine nitrogen give rise to significant increases in the energy barriers to enantiomerization of tetrahedral complexes owing to the steric hindrance involving an intermediate square planar form.     

Photo- and thermochromic spirans. 13. Calculation of the pathways of the thermal electrocyclic reactions of chromenes and their structural analogs by the MINDO/3 method

The mechanisms of the electrocyclic reactions of oxetene (I), 2H-pyran (II), 2-amino-2H-pyran (III), 2H-thiopyran (IV), and chromene (V) in the ground, first singlet, and tripletexcited stateswere studiedby means of the MINDO/3 method. The enthalpies of excitation are 125 (I, S_o), 32 (I, S₁), 113 (I, T₁), 188 (II, S_o), 109 (III, S_o), 150 (IV, S_o), and 239 kJ/mole (V, S_o). The number of isomers of the open form in S_o is determined by the nature of the substituent attached to the final carbon atom. It was observed that donors stabilize both the transoid isomer and the cisoid isomer, which is twisted 20 ° with respect to the formally single - carbon-carbon bond. Bulky substituents cause 105 ° rotation about the same bond.See [1] for Communication 12.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1028–1036, August, 1982.     

Photo- and Ionochromism of Benzoxazolyl-Substituted Spirobenzopyrans

8-Benzoxazolyl-6-formyl-substituted spirobenzopyrans with different acceptor groups in the 5'- position of the indoline moiety have been synthesized. Novel spiropyrans exhibit photochromic properties in an acetone solution at room temperature and form intensely colored complexes with heavy metal cations.     

New Photochromic Salt Spiropyran with Benzyl Substituent

A new salt spiropyran of indoline series containing benzyl substituent in the 8'-position of the [2H]-chromene moiety of the molecule has been synthesized and studied. The structure of the obtained compound has been confirmed by methods ¹H NMR and IR spectroscopy. The study of spectral characteristics and photochromic behavior of the target compound has shown that growing of its single crystal resulted in destruction on account of hydrolysis in acetonitrile. The ¹H NMR spectra of the initial salt spiropyran and product of hydrolysis have been compared.     

A first-order boundary value problem with boundary condition on a countable set of points

LetE={E _n } be the family of subspaces spanning the eigenfunctions and adjoint functions of the boundary-value problem $$ - i\frac{{dy}}{{dx}} = \lambda y, - \alpha \leqslant x \leqslant \alpha , U(y) \equiv \int_{ - a}^a {y(t)} d\sigma (t) = 0$$ that correspond to “close” eigenvalues (in the sense of the distance defined as the maximal of the Euclidean and the hyperbolic metrics). For a purely discrete measuredσ, it is shown that the systemE does not form an unconditional basis of subspaces inL ²(?a, a) if at least one of the end points ±a is mass-free.