Structural studies on polyaza[n]paracyclophanes. A molecular mechanics and crystallographic study

Structural analysis of polyaza[n]paracyclophanes 1-5 has been carried out by the use of molecular mechanics and other techniques. NMR data and molecular mechanics calculations show that conformations in which the polyamine chain is arching above the aromatic ring are prevalent in solution. The crystal structure of triprotonated durene derivative 2b agrees with those studies. Crystals of 3H(+).2b are triclinic, space group <P(1)over bar> with a = 11.758(4) Angstrom, b = 13.870(5) Angstrom, c = 17.181(3) Angstrom, alpha = 96.66(2)degrees, beta = 106.02(2)degrees, gamma = 104.87(3)degrees, Z = 4, R(1) = 0.072, wR(2) = 0.18. Three different conformations are present in the crystal. Good agreement between the crystal structures and calculated conformations is observed, results being more accurate for AMBER* and OPLS* force fields which seem to be the force fields of choice for calculations involving those compounds. Consideration of solvent (GB/SA approach) improves results obtained in calculations.