title: Molecular states of p-dimethylaminobenzonitrile coground with β-cyclodextrin investigated using solid-state fluorescence spectroscopy.
abstract: Changes in molecular states of p-dimethylaminobenzonitrile (DMABN) coground with β-cyclodextrin (β-CD) were examined using solid-state fluorescence measurements. Formation of a DMABN/β-CD inclusion complex by coprecipitation was confirmed by powder X-ray diffraction measurement. The powder X-ray diffraction pattern of the ground mixture was a halo pattern and differed from the pattern of the mixture prepared by coprecipitation. Solid-state fluorescence measurements revealed emission by DMABN crystals in a twisted intermolecular charge-transfer state at 473 nm. DMABN in the DMABN/β-CD coprecipitate had a fluorescence emission peak at 393 nm due to its planar structure. In contrast, DMABN in a DMABN/β-CD ground mixture had an emission peak at 473 nm due to its twisted structure. Grinding time-dependent structural changes in DMABN were evaluated using fluorescence lifetime and relative quantum yield measurements. Structural changes in DMABN in the DMABN/β-CD coprecipitate from a planar to a twisted structure were observed with grinding. DMABN, dispersed in microcrystalline cellulose (CC) molecules in a DMABN/CC ground mixture, had a fluorescence emission peak at 473 nm. However, the excitation spectrum of a DMABN/β-CD ground mixture differed from that of DMABN in CC. These results indicated that the molecular state of DMABN accommodated in the β-CD cavity differs between the coprecipitate and the ground mixture.
authors.affiliation: Faculty of Pharmaceutical Sciences, Josai University, Saitama, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Inoue
authors.forename: Nana
authors.initials: N
authors.lastname: Hasegawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Tozuka
authors.forename: Etsuo
authors.initials: E
authors.lastname: Yonemochi
authors.forename: Toshio
authors.initials: T
authors.lastname: Oguchi
authors.forename: Kenjirou
authors.initials: K
authors.lastname: Higashi
authors.forename: Kunikazu
authors.initials: K
authors.lastname: Moribe
authors.forename: Keiji
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D002482:Cellulose / Q000737:chemistry; D055598:Chemical Phenomena; D004339:Drug Compounding; D055808:Drug Discovery; D005079:Excipients / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009570:Nitriles / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014961:X-Ray Diffraction; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: C115085:4-(n,n-dimethylamino)benzonitrile; D005079:Excipients; D009570:Nitriles; D047392:beta-Cyclodextrins; D002482:Cellulose; C031215:betadex; C109691:microcrystalline cellulose