Isomeric form and proton localization in (9E)-Phenanthrene-9,10-dione[(1Z)- 3,3-dimethyl-3,4-dihydroisoquinolin-1(2H)-ylidene]hydrazonium bromide

(9E)-Phenanthrene-9,10-dione[(1Z)-3,3-dimethyl-3,4-dihydroisoquinolin-1(2H) -ylidene]hydrazonium bromide (LH)Br (I) was synthesized. The models of protonated forms of the LH+ cation were calculated by quantum-chemical methods, and their relative stability was estimated. The crystal structure of compound I was determined by X-ray diffraction analysis. Compound I is built according to the cation-anion type (the mobile protons are located at the nitrogen atoms). The cation exists in the s-cis,cis-isomeric form stabilized by two cyclic hydrogen bonds. The π-electron density is localized on the multiple bonds N(1)-C(1) (1.292(4) Å) and N(3)-C(12) (1.294(4) Å). The spectroscopic characteristics (IR and electronic absorption spectra) of compound I are obtained. © Pleiades Publishing, Ltd., 2010.