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31.
It has been shown previously that bacterial luminescence is reversibly suppressed in vivo and in vitro by both X-rays and hydrogen peroxide. The data presented here show that the mechanisms for this phenomenon is based on the transient oxidation of reduced flavin mononucleotide. 相似文献
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Miljenko Perić Mirjana Mladenović Jasenka Fejzo Christel M. Marian Pablo J. Bruna 《Chemical physics letters》1982,88(6):547-552
The results of an ab initio study of the vibronic and rotational structure in the 2Π state of HNO+ are presented. It is shown that the absorption spectrum at 7200 Å observed by Herzberg could be caused by the transition from the ground to the first excited electronic state of HNO+ 相似文献
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35.
Ubavka B. Mio
Milena Petkovi Milorad Davidovi Miljenko Peri Tyno Abdul-Redah 《Journal of Molecular Structure》2008,885(1-3):131-138
Systematic experimental investigations of heteropoly compounds, particularly their structure and activity, led to the conclusion that most of their characteristics are governed by the presence of protons and protonic entities. Special attention has been paid to two forms of 12-tungstophosphoric acid: hexahydrate (WPA-6) and dehydrated phase (WPA-0). It was postulated that in WPA-6 dynamic equilibrium of protonic entities exists, and that dehydrated phase is stabilized by protons. To confirm the role of the “free protons” or “proton gas” derived on the basis of thermal, structural and spectroscopic experimental studies, we carried out also ab initio calculations on a number of systems containing ion. We were not able to perform direct calculations on the real systems investigated experimentally since the structure of heteropoly compounds is too complex. However, it has been found that ion in WPA-6 definitely is not planar and the results obtained indirectly support the postulated dynamic equilibrium, i.e. possibility of existing of free protons. 相似文献
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Leo tefan Ana iko Robert Vianello Ivica ilovi Dubravka Matkovi-alogovi Miljenko Dumi 《Molecules (Basel, Switzerland)》2021,26(22)
Spontaneous S-alkylation of methimazole (1) with 1,2-dichloroethane (DCE) into 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane (2), that we have described recently, opened the question about its formation pathway(s). Results of the synthetic, NMR spectroscopic, crystallographic and computational studies suggest that, under given conditions, 2 is obtained by direct attack of 1 on the chloroethyl derivative 2-[(chloroethyl)thio]-1-methyl-1H-imidazole (3), rather than through the isolated stable thiiranium ion isomer, i.e., 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium chloride (4a, orthorhombic, space group Pnma), or in analogy with similar reactions, through postulated, but unproven intermediate thiiranium ion 5. Furthermore, in the reaction with 1, 4a prefers isomerization to the N-chloroethyl derivative, 1-chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-thione (7), rather than alkylation to 2, while 7 further reacts with 1 to form 3-methyl-1-[(1-methyl-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8, monoclinic, space group P 21/c). Additionally, during the isomerization of 3, the postulated intermediate thiiranium ion 5 was not detected by chromatographic and spectroscopic methods, nor by trapping with AgBF4. However, trapping resulted in the formation of the silver complex of compound 3, i.e., bis-{2-[(chloroethyl)thio]-1-methyl-1H-imidazole}-silver(I)tetrafluoroborate (6, monoclinic, space group P 21/c), which cyclized upon heating at 80 °C to 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium tetrafluoroborate (4b, monoclinic, space group P 21/c). Finally, we observed thermal isomerization of both 2 and 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8), into 1,2-bis(2,3-dihydro-3-methyl-1H-imidazole-2-thione-1-yl)ethane (9), which confirmed their structures. 相似文献
38.
Miljenko Primorac 《International journal of quantum chemistry》1998,68(5):305-315
We propose a new expansion for the Boys function ∫01t2jexp(−r2t2) dt appearing in the calculation of molecular two-electron matrix elements if Gaussian basis sets are employed. This expansion involves a power series involving the terms Ci, j(τ) (r2−R2)i multiplied by exp(−τr2), where τ is an optimized parameter τ∈[0, 1]. The performances of the introduced expansion are discussed and illustrated by some numerical experiments. It appears that the proposed expansion is considerably shorter than the customary Taylor series, which in turn is the special case for τ=0. This is of some importance, particularly for higher j values. Further, the proposed expansion enables a single expression for calculating erf(x) for the whole range of variable x. The recursive relations for the expansion coefficients are derived and the truncation errors are estimated. A new method for calculating the Boys function by means of asymptotic series is represented too. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 305–315, 1998 相似文献
39.
We test the method of analytic continuation from imaginary to real chemical potential in two-color QCD, which is free from the sign problem. In particular, we consider the analytic continuation of the critical line to real values of the chemical potential. 相似文献
40.
Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees . 相似文献