Enhanced Fluorescence of Remote Functionalized Diaminodicyanoquinodimethanes in the Solid State and Fluorescence Switching in a Doped Polymer by Solvent Vapors

Abstract

Remote functionalized zwitterionic diaminodicyanoquinodimethanes are found to exhibit a dramatic enhancement of light emission in the solid state and when doped in polymer films, as compared to the solution state. Crystal structure analysis of prototypical molecules reveals the role of the remote functionality in the solid state molecular organization. Semiempirical quantum chemical computations provide a viable model to explain the interesting phenomenon of fluorescence enhancement as arising from the inhibition of geometry relaxation of the vertical excited state to a nonemitting state. The reversible switching of a doped polymer film fluorescence triggered by solvent vapors is demonstrated.

Spontaneous Resolution through Helical Assembly of a Conformationally Chiral Molecule with an Unusual Zwitterionic Structure

“…[17] Crystal structure analysis showed that BDPDQI possesses a centrosymmetric lattice belonging to the monoclinic P2 1 /c space group with one molecule in the asymmetric unit. The molecular structure is shown in Figure 1 (left), and the crystallographic details are given in Table 1.…”

“…[17] We have now observed spontaneous resolution through helical organization in crystals of a related molecule decorated with a variety of ionic and potential hydrogen bonding sites. 7-(N,N-dimethylpiperazinium)-7-oxo-8,8-dicyanoquinodimethane (DPODQ) (Scheme 1) possesses cyano groups, an amide group, and a quarternary ammonium functionality capable of participating in hydrogen bonds (O À H¥¥¥N and C À H¥¥¥O) or electrostatic interactions.…”

“…7-(N,N-dimethylpiperazinium)-7-oxo-8,8-dicyanoquinodimethane (DPODQ) (Scheme 1) possesses cyano groups, an amide group, and a quarternary ammonium functionality capable of participating in hydrogen bonds (O À H¥¥¥N and C À H¥¥¥O) or electrostatic interactions. Charge distribution estimated by using a systematic protocol based on semiempirical computations suggests an unusual zwitterionic structure with the negative charge residing on the dicyanomethylene end of the conjugated p-electron system, and a compensating positive charge on the nonconjugated remote [17,18] ammonium functionality. The molecule is conformationally chiral owing to the strong molecular twist between the amide group and the benzenoid ring plane, a feature similar to that found in the precursor DADQ molecules, as well [15±18] ; there are no stereogenic atoms on the molecule.…”

Multisubstituted Olefins: Platform Synthesis and Applications to Materials Science and Pharmaceutical Chemistry

“…If this is the case, aggregation (solidification) should lead to a reduction in the probability and amplitude of molecular motions such as twisting and out-of-plane bending motion, which might trigger radiationless transitions, thereby enhancing the fluorescence efficiency as a whole. Such an aggregation-induced enhanced emission [35][36][37][38][39][40][41][42][43] was also found during the measurements of the photophysical properties of arylethene-based -systems in dioxane/water mixtures. The following example of 14e is typical (Fig.…”

“…26). 18,[35][36][37][38][39][40][41][42][43] For example, as well as highly fluorescent 14, otherwise nonfluorescent -systems such as 15 and 16 also became fluorescent in the solid state. The max values of the solid-state emission were found to be similar to those obtained in chloroform solution.…”