EXCIMER OF CONFORMATIONALLY FLEXIBLE MOLECULES: DIETHYL p-PHENYLENEDIACRYLATE AND METHYL 4-(β-METHOXYCARBONYLVINYL)-α-CYANOCINNAMATE

Abstract

Conformationally flexible molecules of diethyl p-phenylenediacrylate (1) and methyl 4-(β-methoxycarbonylvinyl)-α-cyanocinnamate (2) exhibit excimer emission in concentrated solutions. The excimer of 1 is formed via excitation of the ground state aggregates of 1. In crystalline state, only 2, which has the crystal structure of B-type in Stevens’ classification, being different from the crystal structure (A-type) of 1, gives excimer emission. The stack-type structure is proposed for the excimers of 1 and 2.

Photopolymerization of diolefin crystals

“…42 In a concentrated solution of p-PDAEt in acetonitrile, a stereoselective photodimerization via excimer formation is reported. 43,44 Most of the polymers are easily depolymerized photochemically and thermally in solution to the corresponding monomers, as is expected from the ring cleavage reaction of a number of cyclobutane derivatives yielding two olefins. For example, poly-DSP in solution is rather quickly depolymerized to DSP nearly quantitatively upon photoirradiation40 or by heating above 200 °C.…”

Electrochemical Studies of 1,4‐Bis[2‐(2‐pyridyl)‐vinyl] Benzene and 1,4‐Bis[2‐(4‐pyridyl) vinyl] Benzene Laser Dyes via Cyclic Voltammetry, Convolutive Voltammetry and Digital Simulation Methods

“…19,20 These factors are important in cases where diolefinic dyes undergo molecular association. [21][22][23][24][25] In the present paper we report the electrochemical properties of two diolefinic laser dye compounds namely, 1,4-bis[2-(2-pyridyl)-vinyl] benzene (2PVB) and 1,4-bis[2-(4-pyridyl) vinyl] benzene (4PVB) using cyclic voltammetry combined with convolutive voltammetry and digital simulation techniques. reported for the preparation of this series of diolefinic compounds.…”

Organic photochemistry. XVII. Polymerization of unsaturated compounds by photocycloaddition reactions

“…The rates of polymerization of the cyano esters 169 decreased in the order n-Pr (166) > Me (171) > i-Pr (175) > n-Bu (177) > Et (173). 78 The n-Pr ester 166 polymerized as rapidly as distyrylpyrazine 192 (see section IIG1.).…”

“…78 Changes in the polymerization temperature of between -20 °C and ~+25 °C did not affect the yields or properties of the poly(cyano esters) 170.78 Of all the cyano ester crystals 169, the densities of the Et, n-Pr, and t-Pr ester crystals, 173, 166, and 175 changed the least on polymerization. 78 The Et ester 173 did not polymerize on irradiation in benzene or dioxane solutions.78 Several other compounds, such as the acid, esters, amide, nitrile, and ketone, related to 169 did not polymerize on irradiation in the crystal state.78 3. Bis(a-cyano-j3-arylvinyl)benzenes…”

“…172 The equation for the rate constant in the latter was, k = <x(Topt/T) exp-(-Topt/T), where a is a non-temperature-aependent constant that includes light intensity, quantum yield, etc., and Topt is the optimal temperature at which the maximum rate occurs.172 Topt for 70 was -20 °C.172 Excimer emission from the diethyl ester 70 was observed in concentrated solutions (>0.1 M, MeCN, PhH, or CHC13) but not in the crystal state.173 Activation parameters were reported. 173 The structure of the mirror symmetric dimer, analogous to that of the oligomer 78, formed on irradiating (X > 350 nm) concentrated solutions of 70, was cited as evidence for a stack-type excimer of 70.173 The same dimer was formed by irradiating (X >340 nm) 70 at high concentration; only ground state complexes of 70 were excited.170 At unspecified temperature, the dimer yield increased on increasing the concentration (12% and 34% yields at 5% and 13% concentrations, respectively) whereas it decreased on increasing the temperature (17% and 9% yields at 5 and 45 °C, respectively) at unspecified concentration. 170 The excimer fluorescence intensity and dimer yields changed as functions of concentration of 70 and temperature in similar manners.…”