Naslov
Crystal and molecular structures of diazapyrenes and a study of pi center dot center dot center dot pi interactions

Autori
Kiralj, Rudolf ; Kojić-Prodić, Biserka ; Piantanida, Ivo ; Žinić, Mladen

Izvornik
Acta crystallographica. Section B, Structural science (0108-7681) 55 (1999), 1; 55-69

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
aromatic-hydrocarbons ; 2 ; 7-diazapyrenium cations ; semiempirical methods ; benzene dimer ; Ab-initio ; DNA ; parameters ; optimization ; binding ; model

Sažetak
Two diazapyrenes, 5, 10-dimethyl-4, 9-diazapyrene (1) and novel 2, 7-dimethyl-4, 9-diazapyrene (2) have been synthesized. Their crystal structures are reported here and are the first representatives of diazapyrenes. Crystal data: 1, monoclinic, space group P21/c, a= 4.0246(5)A, b=15.5147(5)A, c=9.1453(9)A, b=101.23(1)o, V=560.1(1)A, Z=2, R=0.043 ; 2, monoclinic, space group C2/m a=12.4968(3)A, b=11.4751(4)A, c=3.9615(5)A, b=96.80(1)o, V=564.09(5) A3, Z=2, R=0.0405. The bond lengths are compared with those calculated by molecular mechanics (MM3), semi-empirical methods (MOPAC 6.0-PM3, AM1, MNDO) and values predicted by valence bond and variableelectronegativity self-consistent field (VESCF) methods. p...p interactions in 1, 2 and seventeen other pyrene and pyrene-like molecules selected form the Cambridge Structural Database [Allen and Kennard (1993). Chem. Des. Autom. News, 8 , 131-137] have been studied. The following quantitative parameters of p...p interactions have been calculated, the shortest crystallographic axis, the offset parameter, the interplanar angle, the interactive volume, and the overlapping surfaces. They are used for the classification of crystal packing motifs ; a high predominance of b, and a few cases of g and sandwich-herringbone types, are observed. In addition, electronegativity, the sum of partial atomic charges of the ring non-H atoms, and the number of aromatic skeleton electrons are used as parameters for classification. MOPAC-PM3 was used for calculations of partial atomic charges in 1, 2, and pyrene analogues. Correlations between geometrical and electronic structure parameters reveal an analogy between the structure of graphite and b type structures.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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