Crystal structure and spectroscopic study of 3,3-dimethyl-3,4-dihydroisoquinolyl-1-carbaldehyde oxime

The crystal structure of 3,3-dimethyl-3,4-dihydroisoquinolyl-1-carbaldehyde oxime (I) was determined by X-ray diffraction analysis (Enraf-Nonius CAD-4 , MoKalpha radiation, graphite monochromator, theta/2 theta scan mode, 2 th eta(max) = 56 degrees, 2927 unique nonzero reflections with I greater than or equal to 2 sigma(I), R = 0.041). Crystals I are monoclinic; a = 9.684(3) , b = 12.072(8), and c = 19.166(8) Angstrom; beta = 100.08(3)degrees; sp. g r. P2(1)/c; Z = 8, V = 2201(1) Angstrom(3); and rho(calc) = 1.334 g/cm(3). Compound I crystallizes in the oxime form as an (E)-s-trans isomer in which the exocyclic and cyclic C=N bonds are trans to each other. Two intermolec ular hydrogen bonds are formed in the crystal between the oxime groups and the cyclic nitrogen atoms of adjacent molecules. One of the hydrogen bonds links independent molecules into pairs, whereas the other bond interlinks t hese pairs into slightly pucked ribbons running along the X-axis. Compound I was characterized spectroscopically. It was shown that, in isopropanol so lutions, the conformation of I becomes intermediate between (E)-s-cis and ( E)-s-trans conformations. The shifts of the long-wavelength bands in the el ectronic absorption spectra of I upon its reaction with CuCl2 or Co(ClO4)(2 ) (Delta lambda(max) approximate to 39-52 nm) indicate the formation of che late complexes, and the shifts observed upon reaction with Co(II), Fe(III), or Cr(III) chlorides or Ag(I) nitrate (Delta lambda(max) approximate to 15 -28 nm) suggest the monodentate coordination of I through the cyclic N atom .