Absorption and fluorescence emission spectral data, as well as fluorescence quantum yields (Φf), were determined for 41p-oligophenylene compounds containing 2-6, 8, and 10 benzene rings. Of 29 compounds containing carbon-bridged rings (fluorenes), 28 were dialkylated on each bridge for improved solubility and photostability. Absorption maxima for oligophenylenes were observed at wavelengths as long as 366 nm, emission maxima to 437 nm, and molar extinction coefficients (ɛ) as large as 153,000 L/mol-cm; all three exceeded predicted maximum values for the corresponding unbridged oligophenylenes. The substitution of furan for benzene or carbazole for a fluorene (two examples each) bathochromically shifted absorption and emission maxima. Dialkylated carbon bridges bathochromically shifted absorption and emission maxima, and lowered Φf in biphenyl and in one terphenyl analogue, but appeared to cause no diminution of Φf in higher oligophenylenes. Bis(2-methoxyethyl) substitution on the bridges, incorporated to provide solubility in polar solvents, lowered Φf in all examples. Tertiary alkyl substituents on terminal rings bathochromically shifted the absorption and emission maxima and generally increased Φf. The "loose bolt" effect, which lowers Φf in mononuclear substituted benzenes, may operate in 9,9-dialkylfluorenes, but not in 2,7-di-t-butylfluorene or in higher oligophenylenes. Cyclic ether and methoxy substituents as auxofluors on terminal rings generally bathochromically shifted absorption and emission maxima and increased ɛ and Φf. Cyano substituents bathochromically shifted absorption and emission maxima, and increased ɛ, but lowered Φf slightly.

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A number of 4-arylpyridines, many methoxy substituted, were prepared by an efficient two-step method involving aryl Grignard addition to 1-methyl-4-piperidone and direct aromatization of the resulting 4-aryl-4-piperidinols. The pyridines were N-alkylated to give sulfonate salts desired for their fluorescent properties. Study of selected compounds as laser dyes revealed several structures to be efficient dyes lasing in the 530-550 nm range. Two new diazaquaterphenyls were prepared and were quaternized. These salts exhibited intense fluorescence in the 420-450 nm range, but would not lase. A phenolic azaterphenyl suitably substituted for excited state intramolecular proton transfer (ESIPT) did not fluoresce at all.

The spectroscopic and lasing characteristics of a series of 308 nm pumped p-oligophenylenes with five or more phenyl rings have been studied. Quantitative comparisons of the absorption spectra of these dyes with numerous other dyes in this class of compounds can be made by defining a parameter, theta, as the sum of the number of phenyl rings and the number of ring-bridges. Statistically good linear regressions result from the correlations of molar extinction with theta and from wavelength of absorbance with the reciprocal of theta. We find that these correlations provide good predictive information in deciding which dyes to attempt to synthesize for testing. The lasing characteristics of the dyes studied show that these dyes are amongst the best dyes in this class of dyes. Some of these dyes have exceptionally long lifetimes coupled with acceptable conversion efficiencies.

Partial bridging of the o,o′ positions of the aromatic rings in quaterphenyl gave superior flashlamp-pumpable laser dyes. Alkyl-substituted carbon bridges gave superior dyes to those containing oxygen or alkyl-substituted nitrogen or silicon bridges. Dyes lasing in the 365–390 nm region with improved energy output, lifetime and solubility were discovered.