Masaharu Akiba

A platinum(II) complex containing carbon-bonded `nitromethane': [Pt(CH2NO2)(2,2′:6′,2″-terpyridine)]+

Abstract X-ray structural analysis disclosed a carbon-bonded nitromethyl platinum(II) complex, [Pt(CH2NO2)(terpy)]+ (terpy=2,2′:6′,2″-terpyridine). The perchlorate salt was readily obtained by adding HClO4 to the nitromethane solution of [Pt(OH)(terpy)]+. The emission spectra of the two salts, perchlorate and tetraphenylborate, are significantly different, suggesting a different extent of the intermolecular interaction between them.

Two-Photon Induced Fluorescence Properties of a Class of Conjugated Ketone Derivatives

We have designed a series of bis(cinnamylidene)cycloalkanone derivatives as two-photon absorption (TPA) compounds that possess a much stronger two-photon absorption induced fluorescence (TPF) than common organic dyes when excited with near-infrared laser radiation. The TPF intensity of the saturated solution of 2,5-bis(p-dimethylaminocinnamylidene)cyclopentanone (DMACCP) excited using a Q-switched Nd:YAG laser at 1064 nm was found to be 11 times larger than that of the most promising TPF compounds. The TPA cross section of the present compounds, as estimated by a fluorescence-based technique, varied from 5×10-50 cm4s/photon for 2,6-bis[3-(9-ethyl)carbazoyl-3-ylidene]cyclohexanone (DMACCH) to 20×10-50 cm4s/photon for DMACCP at an excitation wavelength of 1064 nm.

A new class of light-fast oxonol dyes: organic-glass forming salts of oxonol anions and 4,4′-bipyridinium cations

Light-fastness of anionic oxonol dyes as measured in noncrystalline solid films was markedly improved by introducing 4,4′-bipyridiniums as counter cations.

Two-photon sensitized recording materials for multilayer optical disk

Two types of novel two-photon sensitized recording material writable at 405 nm and 522nm were developed. The fluorescent dye generation type (F-type) material consists of at least two-photon absorption dye (TPAD) and fluorescent dye precursor (FDP), which is non-fluorescent before two-photon recording and fluorescent after two-photon recording due to fluorescent dye generation. The fluorescence quench type (Q-type) material, on the other hand, consists of at least TPAD, fluorescent dye (FD) and fluorescent quencher precursor (QP), which is fluorescent before two-photon recording and the fluorescence intensity is reduced after two-photon recording at the recorded spot due to fluorescent quencher generation. Both types of material showed quadratic dependency of recording light intensity at 522 and 405 nm. A twenty-layer two-photon recording media was fabricated with the Q-type material, and two-photon recording and onephoton fluorescent signal readout was successfully conducted.

A 11?177 Mbps Recordable Digital Versatile Disc (1?16? DVD-R) Using a New Dye

The possibility of 11 to 177 Mbps (1× to 16×) speed recording was confirmed by the investigation of the recordable digital versatile disc (DVD-R) using a new oxonol dye. Low jitter and a high aperture ratio (AR) even after high-speed recording are attributed to the unique thermal decomposition behavior of the dye, i.e., its low decomposition temperature, small heat generation and well defined void generation. The dye neither contains toxic heavy metals nor corrodes a pure silver reflective layer.

Improved Thermal Stability of Dye-Based Optical Discs: Effect of Hydrogen Bonding

To improve the stability of dye-based optical discs during long-term storage, we examined the effect of hydrogen bonding in the dye layer with the expectation that the strong networks of hydrogen bonds would suppress the migration of chemical species, thereby preventing changes in the properties of the amorphous dye films. Intermolecular hydrogen bonding was compared in six dyes, which were composed of a combination of an indodicarbocyanine-dye cation and six colorless naphthalenedisulphonate anions with zero to two hydroxyl groups. Accelerated temperature/humidity testing revealed that the introduction of hydroxyl groups on the colorless anions improved the stability of the cyanine-dye-based optical discs. The error rate was very low, particularly when a thermally stable network of hydrogen bonds involving the hydroxyl (–OH) groups was present, as confirmed by variable-temperature IR spectroscopy. This stabilization due to hydrogen bonding affords a new guideline for designing dyes for optical discs.

SUBSTITUENT EFFECT ON TWO-PHOTON ABSORPTION PROPERTIES OF FLUORENE DERIVATIVES

Two novel fluorene derivatives having cationic substituents were synthesized. Two-photon absorption (TPA) properties of the derivatives were evaluated using the fluorescence-based technique with a femtosecond pulse emitted from a Ti:sapphire laser. Maximum TPA cross-sections of the compounds were estimated from the TPA spectra. Based on the results, the relationship between the TPA cross-sections and the substituent effects of the derivatives were discussed.