Generation of novel materials for nonlinear optics: Analysis of hydrogen-bonded networks in haloaromatic and aliphatic amine-tartrate complexes

Five tartrate-amine complexes have been studied in terms of crystal packing and hydrogen bonding frameworks. The salts are 3-bromoanilinium-L-monohydrogen tartrate 1, 3-fluoroanilinium-D-dibenzoylmonohydrogen tartrate 2, 1-nonylium-D-dibenzoylmonohydrogen tartrate 3, 1 -decylium-D-dibenzoylmonohydrogen tartrate 4, and 1,4-diaminobutanium-D-dibenzoyl tartrate trihydrate 5. The results indicate that there are no halogen-halogen interactions in the haloaromatic-tartrate complexes. The anionic framework allows accomodation of ammonium ions that bear alkyl chain residues of variable lengths. The long chain amines in these structures remain disordered while the short chain amines form multidirectional hydrogen bonds on either side.

Photochemistry of benzylidene-d,l-piperitones in solution and the melt phase

The solution- and melt-phase photochemistry of four trans-benzylidene-d,l-piperitones (1) has been investigated under a variety of conditions. The 1 undergo trans reversible cis isomerization to establish a quasi photostationary state. Further irradiation leads to 2 via oxidative ring closure. Conspicuously absent are dimers (obtained upon irradiation of the neat crystals) and the plausible Norrish Type II photoproducts, 3. Although 1c yields 2c, no evidence for the alternative cyclization route to 2a (requiring loss of HCl) has been observed. Rationalizations for the transformations are presented. The structure of 2b has been determined unambiguously from X-ray crystallographic analysis.

Photodimerization of coumarins in solid cyclodextrin inclusion complexes

The photodimerizations of coumarin and eight of its derivatives are found to proceed selectively in solid inclusion complexes with beta- and gamma-cyclodextrins (beta- and gamma-CD). The distribution of photodimers from these complexes is compared with those from the neat coumarin solids and their solutions in a variety of solvents. By assuming that the stereochemistry of the dimers reflects the packing arrangements of their precursors in the CD complexes, several hypotheses concering the locations and arrangements of the coumarins in the host toruses have been made. The stoichiometries of the complexes have been assigned on the basis of the presence or absence of photodimers and from NMR integration ratios of characteristic coumarin and saccharide protons. The relative orientations of substituted coumarins within a complex are inferred from the stereochemistry of the photodimers. Depending upon the substitution pattern of the coumarin molecules and the type of CD employed, complexes whose guest-host stoichiometries are 1:1, 2:1, and 2:2 have been identified. In several instances, dimers not available from irradiation of neat solid coumarins or their solutions have been obtained from the CD complexes.