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The infrared spectra of C[H.sub.3]Cl [H.sub. 2]O isolated in solid neon at low temperature are examined. High concentration studies of water and subsequent annealing lead to the formation of the ternary C[H.sub.3]Cl:[([H.sub.2]O).sub.2] complex that has a cyclic form in the ground state.

The infrared (IR) spectra of [H.sub.2]O + NO, HDO + NO, and [D.sub.2]O + NO, isolated in solid neon at low temperature is investigated by neon matrix-isolation method combined with IR absorption spectroscopy. The structure of the second observed 1:1 [H.sub.2]O-NO complex has resulted from columbic attractions between water and nitric oxide and it could be stabilized only in matrix, probably by interaction between NO, water and [(Ne).sub.n].

The infrared spectra of the CH3Cl:NO complex isolated in solid neon are investigated detecting most of the vibrational modes of the complex and on the basis of DFT calculations, different geometries are explored for the complex. The weak interaction between NO and CH3CI in CH3Cl:NO is responsible for small shifts of the vibrational mode frequencies of both CH3CI and NO molecules and the most stable structure is of C1 symmetry.

The formation and structure of the CH(sub 3)Cl:H(sub 2)O complex is investigated by neon matrix isolation technique combined with infrared absorption spectroscopy. The complex is found to have a cyclic structure, where the chlorine atom is weakly bonded to one of the hydrogen atoms of water, while the oxygen atom is weakly bonded to one of the hydrogen atoms of CH(sub 3)Cl.

The growing importance of secondary bonded complexes in modern coordination chemistry has given rise to an abundant literature in both experimental and theoretical coordination chemistry. We recently proposed an unified chemical model of secondary interaction enabling to understand the structures in terms of simple chemical rules and concepts. For some complexes the stoichiometry of the electrophilic moiety makes isomerism possible. The problems of isomerism and of the interconversion of isomers are addressed in the present. It is shown, that the reaction mechanisms discussed for pentacoordinated phosphorus derivatives are not suitable for complexes bound by a secondary interaction. The possibility of Berry's pseudo rotations is rejected for this class of systems. [ABSTRACT FROM AUTHOR]

Background: It is not clearly known whether parity can affect the outcomes of starch reduction in the diet of lactating dairy cows. Introduction: A 2 × 2 factorial study was conducted to evaluate the effects of reducing starch in the diets with similar protein and energy contents on lactation performance, ruminal fermentation, nutrient digestibility, behaviour and blood metabolites in primiparous (PP) and multiparous (MP) dairy cows. Methods: Twenty PP cows (DIM = 37 ± 10; 40 ± 5 kg/day of milk; mean ± SD) and 20 MP cows (DIM = 37 ± 9; 48 ± 5 kg/day of milk) were used in present study. Treatments were a factorial arrangement of two levels of starch (high vs. low) and two parity categories (PP vs. MP): (1) high‐starch diet (29.2% ± 0.70) and PP cows (HS‐PP); (2) low‐starch diet (22.3% ± 0.52) and PP cows (LS‐PP); (3) high‐starch diet and MP cows (HS‐MP) and (4) low‐starch diet and MP cows (LS‐MP). All diets were formulated to be similar in crude protein (16.1 % of dry matter) and NEL (1.60 Mcal/kg of dry matter) contents. The amount of metabolise protein was 2688 g/day in high‐starch diet and 2728 g/day in low‐starch diet. The experiment was conducted over two consecutive periods and included 4 weeks for adaptation and 3 weeks for data collection. Results: Dry matter intake and the yield of milk true protein and lactose increased but milk fat: protein ratio and nutrient digestibility decreased for cows fed the HS diets compared with the LS diets. The ruminal proportion of propionate was greater but acetate, the acetate to propionate ratio and sorting against long particles (19 and 8 mm) were lower for cows fed the HS diets than the LS diets. Multiparous cows had a greater nutrient intake and milk yield, longer rumination meal length, greater BW, but lower plasma total antioxidant capacity, non‐esterified fatty acids, faeces pH compared with PP cows. An interaction between parity and the dietary level of starch was detected on feed efficiency measured as FCM yield/DMI in the way that only within PP cows low‐starch diet was more efficient than HS diets. We found another interaction effect of parity × starch on back fat thickens (BFT) change in the way that only within PP cows BFT change was greater for HS compared with LS diet. Conclusion: Overall, regardless of the benefit derived from feeding a reduced‐starch diet by partially replacing grains with sugar beet pulp in the diets on nutrient digestibility, a reduced‐starch diet may be used more efficiently in PP than in MP cows but at expense of body reserves (i.e. BFT) loses. [ABSTRACT FROM AUTHOR]

Beryllium bonding is actually a subclass of secondary bonding. Similar to the case of halogen bonding, the σ- and π-holes on the Be atom of the monomers give in zeroth approximation the direction of electrophilic attack favorable to the formation of beryllium bonds. The nature of beryllium bonding is purely electrostatic so that the symmetry-adapted perturbation theory energy decomposition perfectly explains the relevance of the polarization and dispersion contribution on the formation of the beryllium bond. [ABSTRACT FROM AUTHOR]

The formation of Pd2N2 from the cocondensation of effusive beams of Pd and N2 in neon and argon matrices is evidenced by absorptions in the range of 2200–1800 cm-1. In argon, selective irradiation in the near-infrared and visible ranges leads to interconversions between three structures, distinguished by the stretching frequency of the diatomic N2: Bridged T-shaped (νNN at 1990 cm-1), side on (νNN at 2178 cm-1) and parallel (νNN at 1823 cm-1). For the first two structures, the νNN mode is also accompanied by another signal below 500 cm-1. An extra feature close to 490 cm-1, not sensitive to irradiation at λirr>400 nm and also assignable to a molecule with the same Pd:N2 stoichiometry (2:1), corresponds to a centrosymmetrical Pd–N–N–Pd structure with an inactive νNN mode close to 2141 cm-1, as deduced from the observation of a weak signal close to 2630 cm-1 associated with this species and assignable to the combination νNN+νPdN. All these experimental data and their structural implications are fully supported by theoretical calculations [density functional theory (DFT)]. On the basis of this comparative study, we have obtained a reliable theoretical description of the spectroscopic data using the metageneralized gradient approximation functional within the unrestricted DFT (UDFT) formalism for all spin multiplets. We have also searched a stable electronic solution for each multiplet (particularly for the singlet state), in order to account for the nondynamic correlations. [ABSTRACT FROM AUTHOR]

For the first time the coexistence of a σ- and a π-complex in the C4H4O:HCl system has been observed, in the same supersonic expansion of a molecular jet seeded with argon (or helium) or in a flow-cooled cell at 240 K. This is an exception to the third of the Legon–Miller rules which claims the σ-structure to be the only one to exist. On the grounds of energetic considerations and band contour simulations, two observed bands at 2787.7 and 2795.5 cm-1 of the νs HCl stretching frequency are assigned to the two complexes, recorded as Fourier transform infrared spectra with a resolution between 0.2 and 0.5 cm-1. Complementary calculations show that the use of the standard second-order Mo\ller–Plesset perturbation theory may be erroneous for such a complex, due of the overestimation of the dispersion contribution with respect to the electrostatic term. It is finally established that only a balanced version of the second-order Mo\ller–Plesset perturbation method, spin-component scaled-MP2, or a higher level of theory like a coupled-cluster approach, can provide a reliable energetic analysis for this complex. [ABSTRACT FROM AUTHOR]

Three gas-phase diatomic trications Se23+, Te23+, and LaF3+ have been produced by Ar+ ion beam sputtering of Se, Te, and LaF3 surfaces, respectively. These exotic molecular ions were detected at noninteger m/z values in a magnetic sector mass spectrometer for ion flight times of >=13 μs that correspond to lower limits of their respective lifetimes. Se23+ and Te23+ were unambiguously identified by their characteristic isotopic abundances. Ab initio calculations of the electronic structures of Se23+, Te23+, and LaF3+ show that these molecular trications are metastable with respect to dissociation into fragment ions of Se2++Se+, Te2++Te+, and La2++F+, respectively. Their barrier heights are about 0.49, 0.29, and 0.53 eV, and the equilibrium internuclear distances (bond lengths) are about 0.23, 0.27, and 0.26 nm, respectively. The gas-phase diatomic dications Se22+ and Te22+ were also observed and unambiguously identified. They were found to be long-lived metastable molecules as well, whereas LaF2+ is thermochemically stable. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]