Steven M. Schildcrout

Crystal structure of 9-methacryloylanthracene

In the title compound, the substituted aromatic C atom lies 0.2030 (16) Å out of the anthryl plane, which forms a dihedral angle 88.30 (3)° with the plane of the transoid methacryloyl moiety.

Gaseous cation chemistry and chain‐length effects in electron ionization and collision‐induced dissociation mass spectraof symmetric 1,n‐bis(9‐anthracenyl)alkanes

The behavior of the gaseous cations resulting from EI (30 and 70 eV) of the bichromophoric title compounds 1-5 (for n = 1-5, respectively) is examined by ion-trap mass spectrometry, including collision-induced dissociation (CID) with variation in collision energy. These results are compared with those from anthracene and 9-methylanthracene and with previously reported mass spectrometric results for 3 and dicarbazolylalkanes. Rather than using the kinetic method to obtain ion energetics where the fragmentation mechanism is clear, as commonly done, the method is used here with relative complementary-ion abundances from CID to test the proposed fragmentation mechanisms using B3LYP calculations of relative ionization energies and optimized geometries of ionic and neutral fragments. Hydrogen migrations are common, and skeletal rearrangements including formation of expanded, fused and spiro rings are proposed in several cases. Of the chain cleavages, α-homolysis giving C(15) H(11) (+) , likely as dibenzotropylium, is most important for each of 1-5 except 3, where β-cleavage to C(16) H(13) (+) dominates with a proposed methyldibenzotropylium structure. α-Cleavage was important also in the dicarbazolylalkanes. A previous inference of a McLafferty rearrangement to explain C(15) H(12) (+•) from 3 is not supported by the present results. The fragmentation behavior of 1-5 depends strongly on n and implies significant interchromophoric interaction between anthracenyl groups.

Structure and Properties of 9,14,15,16,17,18,19,20-Octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene

The compound 9,14,15,16,17,18,19,20-octahydro-9,14[1′,4′]-benzenobenzo[b]triphenylene, C28H24, was prepared by hydrogenation of the photocycloadduct of dibenz[a,c]anthracene and 1,3-cyclohexadiene with Pt/C in ethyl acetate. The X-ray diffraction analysis shows that the compound crystallizes in the monoclinic space group with the geometric parameters of = 11.0090(17) A, = 13.733(2) A, = 13.091(2) A, and = 109.583(13)°. In addition to several close intramolecular contacts involving hydrogens derived from the dibenzanthracene moiety, long interannular C–C single bonds of about 1.593 A are present. These bonds are shorter by about 0.18 A than the corresponding bonds in the unsaturated precursor, which can be attributed to reduced strain in the more saturated polycyclic ring system. Anisotropic shielding of the four endo-methylene hydrogens in the 1H NMR spectrum is larger for the two hydrogens lying above the phenanthrene unit, which resonate at 1.03 ppm, than those above the benzenoid ring, which resonate at 1.24 ppm. Theoretical calculations reproduce the geometry with good agreement.