Reactivities of Carboxyalkyl-Substituted 1,4,5,8-Naphthalene Diimides in Aqueous Solution

Abstract

A series of water-soluble 1,4,5,8-naphthalene diimide derivatives has been prepared and their redox and photophysical properties characterized. From laser flash photolysis studies, the triplet excited state of N,N'-bis[2-(N-pyridinium)ethyl]-1,4,5,8-naphthalene diimide (NDI-pyr) was found to undergo oxidative quenching with the electron donors DABCO, tyrosine, and tryptophan as expected from thermodynamics. Interestingly, the reactivities of naphthalene diimides (NDI) possessing alpha- and beta-carboxylic acid substituents (R = -CH2COO-, -C(CH3)2COO-, and -CH2CH2COO-) were strikingly different. In these compounds, the transient produced upon 355 nm excitation did not react with the electron donors. Instead, this transient reacted rapidly (k > 10(8)-10(9) M-1 s-1) with known electron acceptors, benzyl viologen and ferricyanide. The transient spectrum of the carboxyalkyl-substituted naphthalimides observed immediately after the laser pulse was nearly identical to the one-electron-reduced form of 1,4,5,8-naphthalene diimide (produced independently using the bis-pyridinium-substituted naphthaldiimide). From our studies, we conclude that the transient produced upon nanosecond laser flash photolysis of NDI-(CH2)nCOO- is the species produced upon intramolecular electron transfer from the carboxylate moiety to the singlet excited state of NDI. In separate experiments, we verified that the singlet excited state of NDI-pyr does, indeed, react intermolecularly with acetate, alanine, and glycine. The process is further substantiated using thermodynamic driving force calculations. The results offer new prospects of the efficient photochemical production of reactive carbon-centered radicals.

Controlling the crystalline three-dimensional order in bulk materials by single-wall carbon nanotubes

“…The presence of carboxylates and Na þ -from the basic soft conditions-complexes might influence the highest occupied molecular orbital/lowest unoccupied molecular orbita levels of the corresponding electroactive species, namely, exTTF and SWCNTs, or might even interact with them through anion-p or cation-p interactions 55,56 . However, our investigations reveal that on photoexcitation, localized exTTF-and SWCNT-excited states evolve and transform rapidly into well-characterized electron transfer products ruling out any major impact.…”

Amino Acid Derivatized Arylenediimides: A Versatile Modular Approach for Functional Molecular Materials

“…The molecular organization of 8 and 9 were attributed to hydrogen bonds between the carboxylic acid termini and the hydrophobic contacts between the NDI cores. In another report, such NDI bolaamphiphiles having α‐ and β‐carboxylic acid termini were reported to produce reactive radical intermediates by a new mechanism 20. The proposed mechanism conveys rapid production of the one‐electron‐reduced NDI, via intramolecular electron transfer from the covalently attached carboxylate group.…”

Ultrafast Photoinduced Charge Separation in Naphthalene Diimide Based Multichromophoric Systems in Liquid Solutions and in a Lipid Membrane

“…The photophysics of N-substituted NDIs has already been investigated in detail. [22][23][24][25][26][27][28] These compounds are colorless, their first absorption band being located below 400 nm, and very weakly fluorescent because of fast intersystem crossing favored by the strong spin-orbit coupling introduced by the carbonyl groups. N-Substituted NDIs are often used as building blocks in dyads, triads, and donor-bridge-acceptor systems where they act as electron acceptor, [29][30][31][32][33] but their fast intersystem crossing prevents their use as light absorbers.…”