NIR-Sensitized Activated Photoreaction between Cyanines and Oxime Esters: Free-Radical Photopolymerization.

Cyanines comprising either a benzo[e]- or benzo[c,d]indolium core facilitate initiation of radical photopolymerization combined with high power NIR-LED prototypes emitting at 805 nm, 860 nm, or 870 nm, while different oxime esters function as radical coinitiators. Radical photopolymerization followed an initiation mechanism based on the participation of excited states, requiring additional thermal energy to overcome an existing intrinsic activation barrier. Heat released by nonradiative deactivation of the sensitizer favored the system, even under conditions where a thermally activated photoinduced electron transfer controls the reaction protocol.

The effects of substituents and solvents on the ground-state π-electronic structure and electronic absorption spectra of a series of model merocyanine dyes and their theoretical interpretation.

Two series of new merocyanine dyes have been synthesised and the dependence of their electronic structure on substituents and solvents has been studied by NMR spectroscopy, by using both the NMR (13)C chemical shifts between adjacent C atoms in the polymethine chain and the (3)J(H,H) coupling constants for trans-vicinal protons. The widely used valence bond (VB) model based on two contributing structures cannot account theoretically for the observed alternating π-electron density in the polymethine chain. In addition, the prediction of zero-π-bond order alternation (or zero-bond length alternation) by this model is also incorrect.

Long-wavelength absorbing and fluorescent chameleon labels for proteins, peptides, and amines.

Long-wavelength absorbing labels that change their color and fluorescence upon conjugation to proteins and other biomolecules provide two critical advantages over the wealth of conventional amine-reactive labels. At first, the progress of the labeling reaction can be monitored continuously either visually or by spectrometry without prior purification. Then, the labeled biomolecule can be investigated with red or near-infrared light, which minimizes background interference in biological samples.

Relationship between the molecular structure of cyanine dyes and the vibrational fine structure of their electronic absorption spectra.

Electronic absorption spectra of symmetrical cyanine dyes show vibronic sub-bands, attributed to the symmetric C-C valence vibration of the polymethine chain in the electronic excited state. Displacements in the equilibrium configuration between electronic ground and excited states of cyanine dyes lead to longer C-C bonds in the excited state. Additionally, in the electronic ground state, a small degree of bond localisation always remains in the chain depending on the different heterocyclic terminal groups.

Structure property analysis of pentamethine indocyanine dyes: identification of a new dye for life science applications.

A collection of nine pentamethine indocyanine dyes was synthesized, and the photophysical characteristics relevant to applications in cell biology and single molecule detection were analyzed in detail. Substituents at the aromatic system covering the auxochromic series and substitutions in the polymethine chain were investigated with respect to absorption and emission spectra, fluorescence lifetimes, fluorescence quantum yields, and fluorescence autocorrelations. Substitutions in the polymethine chain increased the nonradiative energy dissipation of the excited singlet state and decreased the fluorescence quantum yield, relative to the unsubstituted compound.