Synthesis, Crystal Structure And Properties Of New Organic Heterocyclic Two-photon Materials

Recently, organic materials exhibiting large two-photon absorption (TPA) behavior have received considerable interest because of their various applications such as optical power limiting up-converted lasing, two-photon fluorescence excitation microcopy, three-dimensional optical data storage, photodynamic therapy, and microfabrication.The two-photon absorption compound 2-[4- (Isopho-rone-vinyl)phenyl]imidazo [4,5-f][1,10]phenanthroline (abbreviated as FPIP) has been synthesized through four-step reaction, whose two-photon absorption cross-section was obtained by two-photon excited fluorescence technique. The solvent effect is explained by the "twisted intra-molecular charge transfer" (TICT) model. The photophysical behavior in neutral and acidic/basic ethanolic (or THF) was studied using UV-Vis spectrometry, one and two-photon fluorescence spectroscopy. The fluorescence of FPIP can be made to respond strongly to changes in PH in solution. In basic condition, the fluorescence of FPIP increased while in acidic condition, the fluorescence of FPIP decreased. Which can be seen that the compound FPIP was a potential two and one photon excited fluorescence-optimized molecular probe. Furthermore, FPIP can be seen as a prototypes of pH-sensitive two-photon excited fluorescence (TPEF) compoud containing imidazole.One new type imidazo ligand (IPVB)was synthesized, and its linear optical properties were measured. Besides NLO field, the using of the ligand can be found in the field of supermolecular chemistry and crystal engineering.The linear absorption, one and two-photon induced fluorescence is experimentally studied. Some conclusions were listed as follows:(1) The maximum fluorescence peaks including one photon fluorescence clearly show a slight red-shift and the fluorescence intensity show a slight decrease with the increase of the polarity of the solvent.(2) Different charge transfer behavior of FPIP in acidic, basic and neutral condition result in a large difference in fluorescence behavior. In basic condition, the FPIP have the largest electronic density and its fluorescence was increased. In acidic condition, the FPIP have the small electronic density, and its fluorescence was decreased.(3) The maximum peak positions of the two-photon fluorescence spectra forcompound FPIP show a slightly red-shift compared to that of one-photon fluorescence which can be explained by the reabsorption of the dye.The equilibrium geometry and the excited state calculation (ZINDO) of neutral, basic and acid FPIP molecular were performed based on the trans orientation. The conjugated geometric configuration and the electron density distribution of the frontier molecular orbitals reveal that the molecule has a highly delocalized n -electron system, These structural features are necessary for large two-photon absorption.Four crystal structures were determined by X-ray single crystal diffraction analysis. The X-ray diffraction data of single crystals were collected on a Bruker P4 four-cycle diffractometer. The relationships between the structures and properties of them can be discussed on the crystal diffraction analysis.The triphenylamine derivatives N, N , N', N'-tetraphenyl-(l, l'-biphenyl) - 4, 4'-diamines and N, N, N', N' -tetraphenyl-1, 4-benzenediamine, as two important hole transporting materials for electroluminescent devices, were synthesized by using methane sulfonic acid (CH3SO3H) as catalyst. Other oligomeric derivatives can be expected obtained using this new method. The crystal structures of these two compounds are discussed. All the N atoms are sp2-hybridized and the lone electron pairs are involved in conjugation with phenyl moieties. All the N-C bonds spread almost symmetrically from the N atom.The conclusions from this work are helpful for the design and synthesis of new heterocycle molecules contained imidazole with strong TPA properties.