This thesis explores substituent effects on the photochromism of the benzo[e]dimethyldihyropyrene system 3. Thus systems with conjugated connectors, (25, 29, 33, 34), a system with conjugation and then insulating connector (31), one with an organometallic connector (32), and a system functionalized on the benzene ring (35), were synthesized and their photochemical studies were carried out. Comparisons of the photo opening and closing rates relative to benzo[e]pyrene 3 under similar conditions were performed. All the derivatives of 3 synthesized (except for the ferrocenyl product 32) had faster visible opening rates than the parent 3; the UV closing rates for most of the derivatives were are almost the same as that of the parent 3. Several linked photochromes having two photochromic units have been successfully synthesized from their monomeric precursors using metal mediated coupling reactions. Both photochromic units of the bis-switches, 41 and 54 open and close, although it is not possible to address each photochrome independently. UV closing of the open-open forms of the bis-photochromes occur via the open-closed intermediate. Thus 41 and 54 act as multiple state switches. In the case of 49 only one photochromic unit of the bisphotochrome opened. However, none of the photochromic units in 38 opened. The thermal return reactions (cyclophanediene to dihydropyrene) were studied on the benzo[e]dihydropyrene derivatives and linked bis-photochromic systems and the energy of activation of the thermal reversal and the half-lives were determined to be similar or 1- 2 kcallmol less than the benzo system 3.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

This thesis focuses on the investigation of the optoelectronic, photo and thermal- responsive properties of organoboron compounds. In search of blue phosphors for phosphorescent organic light emitting diodes, new triarylboron functionalized phosphorescent Pt(II) complexes were synthesized and their device performances were evaluated. In Pt(II) complexes with the 2-phenylpyridyl N,C-chelate ligand and an acetylacetonato ancillary ligand, it was found that BMes2 substitution at the 4’ position of the phenyl ring can increase the phosphorescent emission energy, compared to the 5’-BMes2 substituted analogue. This occurred without substantial loss of luminescent quantum efficiency. At 100 cdm-2 luminance, electroluminescence devices with the newly synthesized Pt(II) complexes as emitters have achieved external quantum efficiency of ~ 4.7-13.4%. Tuning of the photo-responsive properties of biaryl N,C-chelate dimesitylboron compounds was achieved by functionalization with either a bisthienyl moiety or ferrocene unit. It was demonstrated that the bisthienyl unit has the ability to completely stabilize a N,C-chelate boryl chromophore toward photoisomerization. With the ferrocene unit being part of the chelation backbone of BMes2 moiety, the B−N bond of molecule B(2-ferrocenyl-N-Me-benzimidazolyl)Mes2 was found to undergo a dynamic dissociation/association process in solution, leading to its slow hydrolysis under ambient conditions. The oxidized ferrocenium species has a notable spin delocalization through space from the Fe(III) center to a flanking mesityl group. To further expand the photochromic family based on pyridyl N,C-chelate dimesityboron compounds, a systematic study was carried out with the pyridyl N donor replaced by N-heterocyclic carbene donor and azolyl, benzoazolyl N donors. These new classes of organoboranes all underwent transformation to their corresponding dark isomer in a similar fashion as the pyridyl N,C-chelate dimesitylboron. However, a second-step photoisomerization was observed in the NHC,C-chelate dark isomer via a “borylene”-like intermediate. The thiazolyl, benzoazolyl N,C-chelate dark isomers demonstrate multi-structural transformations, which include hydrogen atom transfer, 1,3-boryl shift and diastereomer interconversion via a spiropyran type ring-opening/closure process. The imidazolyl N,C-chelate dark isomer exhibits a consecutive photochromism phenomenon, namely an interconversion between azaboratabisnorcaradiene and azabenzotropilidene derivatives. The calculated mechanism for this bares an interesting resemblance to that of the “walk” rearrangement in norcaradiene. / Thesis (Ph.D, Chemistry) -- Queen's University, 2014-06-23 20:55:20.399

Thesis (M.S.)--Rochester Institute of Technology, 1986. / Typescript. Includes bibliographical references (leaves 43-44).

Tricyanofuran-type metastable-state photoacids, relative newcomers to the field of photochromism, outperform traditional light-controlled molecular switches in regards to applicability in biological systems. In a preliminary attempt to understand the underlying processes that govern these compounds, this thesis project establishes the isomeric identity of an unsubstituted tricyanofuran-type metastable-state photoacid, referred to as TCF 1 in this work. Two-dimensional nuclear magnetic resonance experiments are employed to experimentally determine the presence and identity of the open-form TCF 1 isomers. Electronic structure calculations are then used to provide quantitative insight into the experimental results. Experiment and theory show that four out of eight possible open-form isomers exist in solution. To validate the information obtained theoretically, the calculation methodologies are tested against experimental chemical shifts. The impressive agreement with the experiments gives credibility to the picture painted by the theoretical models.

Fluorescence microscopy offers the opportunity to image noninvasively biological samples in real time. However, the phenomenon of diffraction limits the resolution of conventional fluorescence microscopes to submicrometer dimensions in both the horizontal and vertical directions. This limitation can be overcome by photoswitchable fluorescent probes able to undergo reversible saturable optically linear fluorescence transitions (RESOLFT). In this study, firstly, a photoswitchable fluorescent probe based on BODIPY fluorophore and Spiropyran photochrome were designed and its photophysical and photochemical properties were investigated in organic and aqueous environments. Also, its imaging with patterned illumination was showed by trapping them in PMMA matrix. Secondly, photochromic [1,3]oxazines with different substituents as well as polymers incorporating them were synthesized and their photochemical and photophysical properties were investigated. Thirdly, to improve the switching speeds and fatigue resistance of the BODIPY-Spiropyran conjugate, the photochromic part was replaced by [1,3]oxazines and dyads incorporating BODIPY fluorophore and [1,3]oxazine photochromes were synthesized. Lastly, a new strategy was designed to switch the fluorescence of fluorophores by a modular approach. It is based on photoinduced elongation of the absorption wavelength of a fluorescent chromophore with the aid of an appended photochromic auxochrome.