Ma. Eugenia Ochoa

New perspectives for boronic esters in macrocyclic chemistry

In the present contribution a tetrameric macrocyclic compound derived from 2,6-pyridinedimethanol and 3-nitrophenyl boronic acid, as well as 10 new dimeric boronates prepared from 2-salicylideneaminoethanol and different aryl boronic acids such as a 2-methylphenyl-, 3-methylphenyl-, 4-methylphenyl-, 3-methoxyphenyl-, 4-methoxyphenyl-, 3-chlorophenyl-, 4-chlorophenyl-, 3-nitrophenyl-, 3-trifluoromethylphenyl- and 4-fluorophenylboronic acid are described. The tetrameric and three of the dimeric structures have been analyzed by X-ray crystallography, and a series of parameters such as bond length, bond angles, deviation of the boron atom from the boronate mean plane and intermolecular interactions are discussed.

Synthesis, Characterization, and Rotational Dynamics of Crystalline Molecular Compasses with N-Heterocyclic Rotators

We describe in this paper the synthesis, crystallization, and solid-state NMR dynamics of molecules intended to emulate the structure and function of macroscopic compasses. The desired structures consist of polar pyridine (2) and pyridazine (3) groups as well as their corresponding N-oxides (2O and 3O), each linked axially to two bulky triphenyl methyl groups by 1,4-triple bonds. The structures are such that the central polar heterocycles may rotate about the dialkyne axle while being sterically shielded by the two trityl groups. In addition to the synthesis of samples with natural isotopic abundance, we describe the preparation of 2-d(2) and 3-d(30), one labeled with deuteria in the pyridine rotator and the other fully deuterated in the two trityl groups in the stator. Crystal structures of 2 and 3 revealed packing motifs analogous to those previously reported for samples prepared with substituted phenylene rotators. While solid-state NMR measurements by (13)C CPMAS NMR revealed insufficient chemical shift dispersion for a dynamic characterization of the rotation of compounds 2 and 3 (including 3-d(30)), the use of quadrupolar echo (2)H NMR methods with 2-d(2) revealed a rotational site exchange with a barrier of ca. 8.5 kcal/mol (35.5 kJ mol(-1)) for the pyridine group in 2.

Synthesis and non-linear optical characterization of novel borinate derivatives of cinnamaldehyde

Herein is reported the synthesis of three new borinates (2a–2c) derived from bidentate imine ligands (1a–1c), which were prepared from the corresponding cinnamaldehyde derivatives. All compounds were characterized by MS, IR and NMR spectroscopy. The nonlinear optical (NLO) characterization of these molecules having push–pull properties is included. Second order nonlinearities were evaluated at 1.907 μm by the electric-field-induced second harmonic (EFISH) technique through the β×μ product, showing a trend for a general increase of the NLO response after boron complexation. For borinate 2c, which has strong electron-donating and electron-withdrawing groups at opposite ends of the π-backbone, βμ = 1560 × 10−30 D cm5 esu−1, showing a three-fold increase with respect to the ligand 1c (βμ = 542 × 10−30 D cm5 esu−1). Third-order nonlinearities, in solid films, were evaluated employing the third harmonic generation (THG) Maker Fringe technique showing χ(3) susceptibilities of the order of χ(3)∼10−12 esu at the infrared wavelength of 1.2 μm. Compounds with the highest χ(3) values correspond to those having the largest βμ product: for 1cχ(3) = 1.1 × 10−11 esu and for 2cχ(3) = 8.4 × 10−12 esu.

Facile synthesis of 1,3,6-oxadiazepines from 2,2′-(1,2-ethanediyldiimino)bisphenols

Abstract A useful sequence of reactions for the syntheses of a variety of heterocyclic systems including an oxadiazepine ring is described. The key step involves the condensation of substituted 2,2′-(1,2-ethanediyldiimino)bisphenols with ethanedial to provide stereoselectively the 6a,7a-trans-6,6a,7a,8,15,16-hexahydro[1,4]benzoxazine[4′,3′:6,7][1,3,6]oxadiazepino[2,3-c][1,4]-benzoxazine-6,8-diol framework, as established by X-ray diffraction analyses.

CCDC 1582960: Experimental Crystal Structure Determination

Related Article: Ma. Eugenia Ochoa, Pablo Labra-Vazquez, Norberto Farfan, Rosa Santillan|2018|Cryst.Growth Des.|||doi:10.1021/acs.cgd.7b01542