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The excited singlet of trans-3-aminostilbene and its N-methyl derivatives are strongly fluorescent in cyclohexane solution and have large singlet state dipole moments. Addition of low concentrations of alkylamines results in a continuous red shift of the emission maximum and decreasing fluorescence intensity.

The structure, spectroscopy and photochemistry of N,N'-dimethyl-N,N'-di-1-naphthylurea is studied, and the properties of the corresponding secondary diarylurea N,N'-di-1-naphthylurea are compared with the tertiary mono arylurea N,N,N'-trimethyl-N'-1-naphthylurea. The characterization of the spectroscopy and photochemistry of the conformations are performed due to the preferred folded geometry.

The molecular structure, absorption, and fluorescence spectra of N,N'-dimethyl-N,N'-di-l-pyrenylurea and N,N'-dimethyl-N,N'-di-2-pyrenylurea have been investigated and compared to the properties of N,N,N'-trimethyl-N'-pyrenylurea model compounds. Di-l-pyrenylurea exists as a mixture of folded (E,E) syn- and anti-rotamers that interconvert via flipping of one of the pyrene rings to an unfolded (E,Z) geometry. The symmetric di-2-pyrenylurea exists as a single folded (E,E) conformation which is in equilibrium with a less-stable, unfolded (E,Z) rotamer. The absorption and fluorescence spectra of the dipyrenylureas at 77 K in a rigid glass are similar to those of monopyrenylurea model compounds. However, in fluid solution, the dipyrenylureas exhibit excimer fluorescence and very weak monomer fluorescence which have identical decay times. This behavior is attributed to fast rotational equilibrium between folded rotamers which exhibit excimer fluorescence and unfolded rotamers which exhibit monomer fluorescence. The behavior of the dipyrenylureas is compared with that of other systems that form intramolecular pyrene excimers and diarylureas. Key words: excited state rotamers, dipyrenylureas, pyrene excimers, ureaphane.

Free energy change that controls electron transfer from the anion radical of perdeuterated [16]annulene to neutral [16]annulene has been demonstrated by means of X-band EPR measurements. Results indicate qualitative agreement between experimental and theoretical values.

The syntheses, structures and spectroscopy of a series of oligomeric tertiary oligophenylureas possessing one to five phenyl rings are reported. It is concluded that the nature of the electronic interactions within the oligophenylureas is influenced by an unusual folded geometry in which the phenyl rings adopt a splayed face-to-face relationship.

The diarylurea anion radical undergoes a novel intramolecular reductive elimination, wherein the overlapping p(sub pi) orbitals on the ipso carbons of opposing aryl groups evolve into a sigma bond, forming the biaryl anion radicals. The reductive dimerization of diarylureas offers a method for the synthesis of both symmetric and nonsymmetric biaryls.

Formation and behavior of fluorescent Lewis acid-based exciplexes and triplexes are examined.

Evidence for isomeric forms of (16)-annulene and (18)annulene with differing internal hydrogen spatial arrangements is presented.

The synthesis of perdeuterated (16)annulene produced material that 95% atom deuterated. The deuterated (16)annulene-d15 was compared with the perdeuterated (16)annulene. The results showed that deuteration allowed the flattening of the 16-membered ring. In addition, deuteration allows the increase in the actual aromatic and antiaromatic characters of the neutral and dianionic systems, respectively.