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The reactivity of a B3P3-doped hexa-cata-hexabenzocoronene, as a model of nanographene (B3P3-NG), towards carbon dioxide was studied at the DFT M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G* level of theory. This compound can be classified as a poly-cyclic poly-Frustrated Lewis Pair (FLP) system, as it presents more than one Lewis Acid/Lewis Base pair on its surface, making the capture of several carbon dioxide molecules possible. Two scenarios were considered to fully characterize the capture of CO2 by this multi-FLP system: (i) fixation of three CO2 molecules sequentially one by one; and (ii) simultaneous contact of three CO2 molecules with the B3P3-NG surface. The resulting adducts were analyzed as function of activation barriers and the relative stability of the CO2 capture. A cooperativity effect due to the π-delocalization of the hexa-cata-hexabenzocoronene is observed. The fixation of a CO2 molecule modifies the electronic properties. It enhances the capture of additional CO2 molecules by changing the acidy and basicity of the rest of the boron and phosphorus atoms in the B3P3-NG system. [ABSTRACT FROM AUTHOR]

Ab initio equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculations have been carried out to evaluate spin-spin coupling constants in six pairs of homo- and hetero-chiral dimers: [(HOOH).sub.2],[([H.sub.2]NN[H.sub.2]).sub.2], [(FOOH).sub.2], (FHNN[H.sub.2]).sub.2], [(HOOOH).sub.2], and [(FOOOH).sub.2]. Corresponding spin-spin coupling constants in these isomeric pairs of [C.sub.2] and [C.sub.i] symmetry may differ, but these differences are small and may not be detectable experimentally. For the complexes with O1-H ... O and O1-H ... F hydrogen bonds, ¹J(O1-H) has a larger absolute value in the [C.sub.2] isomer. For the same set of complexes, ¹/(O1-O2) has a larger absolute value in the [C.sub.i] isomer. No distinguishable patterns could be discerned in the remaining spin-spin coupling constants in the [C.sub.2] and [C.sub.i] isomers of these complexes, nor in complexes with N-H ... N hydrogen bonds. Key words: spin-spin coupling constants, homo- and hetero-chiral dimers, hydrogen bond. Des calculs ab initio EOM-CCSD ont ete effectueis pour eevaluer les constantes de couplage spin-spin dans six paires de dimeres homo- et heterochiral : [(HOOH).sub.2],([H.sub.2]NN[H.sub.2])2, [(FOOH).sub.2], (FHNN[H.sub.2]).sub.2], [(HOOOH).sub.2], et [(FOOOH).sub.2]. Les correspondantes constantes de couplage spin-spin dans les paires d'isomeres sont, en general, diffeerentes mais les differences sont faibles au point, pour certaines d'entre elles, de ne pas pouvoir etre detecteees experimentalement. Pour les complexes avec des liaisons hydrogene O-H ... O et O-H ... F, ¹/(O1-H) a une plus large valeur absolue dans l'isomere [C.sub.2]. Pour le meme ensemble des complexes, ¹/(O1-O2) a une plus large valeur absolue dans l'isomere [C.sub.i]. On ne trouve pas des regles generales pour les restantes constantes de couplage spin-spin dans les isomeres [C.sub.2] et [C.sub.i] de ces complexes et non plus dans les complexes avec des liaisons hydrogene N-H ... N. Mots-cles: constantes de couplage spin-spin, homo- et hetero-chiral dimeres, liaisons hydrogene., Introduction Chiral distinction or 'chiral recognition' has been a topic of interest to both theorists and experimentalists. In the past, we have devoted several papers to the topic of chiral [...]

The synthesis of a series of atropisomeric iminothiazolines is carried out by using methoxy precursors. The reaction provides insight into stereodynamics of hydrogen bond between the proton of the OH group and the nitrogen of the imino group.

The characteristics of the intramolecular hydrogen bond (IMHB) were systematically analyzed for a series of 40 different enols of [beta]-diketones and their nitrogen counterparts. The findings indicated that the resonance-assisted hydrogen bond (RAHB) effect is not the primary reason behind the strength of their IMHBs.

Ab initio calculations are performed to determine the structures and binding energies of open and cyclic complexes formed from the [sp.sup.2] [[H.sub.2]C=PH and HP=PH (cis and trans)] and [sp.sup.3] [P[H.sub.2](C[H.sub.3]) and P[H.sub.3]) hybridized phosphorus bases and their corresponding protonated ions. The experimental measurements of [super 2h][J.sub.p-p] are able to differentiate between open and cyclic complexes.

The cationic interactions of chromium complexes are calculated. The dual binding to cations and anions is exhibited in these complexes.

Ab initio equation-of-motion coupled-cluster singles and doubles method (EOM-CCSD) calculations are carried out on molecules [H.sub.m]X-Y[H.sub.n] for X, Y = [super 15]N, [super 17]O, [super 31]P and [sup.33.S] in order to investigate the variation of one-bond X-Y spin-spin coupling constants [super 1]J(X-Y) and components of J with rotation about the X-Y single bond. It is found that the reduced Fermi-contact terms for all the molecules are negative and decrease in absolute value as the rotational angle [theta] changes from zero degree.

Ab initio calculations are used to analyze the interactions between nitrous oxide and a series of small and large molecules that act simultaneously as hydrogen bond donors and electron donors. The results have indicated that the [N.sub.2]O molecule can form up to three interactions, thus opening the possibility to design [N.sub.2]O abiotic receptors.