Bis(BF₂)‐2,2′‐Bidipyrrins (BisBODIPYs): Highly Fluorescent BODIPY Dimers with Large Stokes Shifts

Abstract

Four new dimeric bis(BF(2))-2,2'-bidipyrrins (bisBODIPYs), and their corresponding BODIPY monomers, have been prepared and studied with respect to their structural and photophysical properties. The solid-state molecular structure of the dimers and the relative orientation of the subunits have been revealed by an X-ray diffraction study, which showed that the molecules contain two directly linked BODIPY chromophores in a conformationally fixed, almost orthogonal arrangement. Two of the fluorine atoms are in close contact with each other and the (19)F NMR spectra show a characteristic through-space coupling in solution. The new chromophores all exhibit a clear exciton splitting in the absorption spectra with maxima at about 490 and 560 nm, and are highly luminescent with an intense emission band at around 640 nm. The Stokes shift, which is the difference between the maximum of the lowest-energy absorption band and the maximum of the emission band, has a typical value of 5 to 15 nm for simple BODIPYs, whereas this value increases to 80 nm or more for the dimers, along with a slight decrease in fluorescence quantum yields and lifetimes. These properties indicate potential uses of these new fluorophoric materials as functional dyes in biomedical and materials applications and also in model compounds for BODIPY aggregates.

Functional Porphyrinoids from a Biomimetically Decorated Bipyrrole

“…Solvents were dried prior to use by standard procedures and stored under argon in the dark. 5,5Ј-Diformyl-3,3Ј-bis(methoxycarbonylethyl)-4,4Ј-dimethyl-2,2Ј-bipyrrole (1), [15] 3,4-diethyl-2-methylpyrrole (2) [21] and 3-ethyl-2,4-dimethylpyrrole (3) [22] were prepared as described previously. NMR spectra were obtained with a Bruker ARX-300 or a Bruker DRX 400 spectrometer.…”

“…2,2Ј-Bidipyrrins are versatile open-chain tetrapyrroles. [14] They have been employed in the preparation of novel fluorophors, [15] as ligands in helical transition-metal complexes, [16] in helicates, [17] and in polynuclear complexes, [18] and can be used as precursors in the template-assisted oxidative macrocyclization to corroles [19] and other macrocyclic non-natural porphyrinoids.…”

“…Bis-(bodipy)s [15] are novel covalent dimers of the well-known bodipy fluorophors [28] with advantageous photophysical properties. [29] Compound 7 was prepared from 5 and BF 3 / etherate by the optimized procedure described earlier, [15] as a dark green powder in 21 % yield (Scheme 2). Compound 7 is highly fluorescent in solution even upon excitation by ambient light, and solutions of the new compound always appear red because of the emitted photons.…”

Theoretical study on photophysical properties of novel bis(BF2)‐2,2′‐bidipyrrins dyes: Effect of variation in monomer structure

“…Structures of all the studied models are illustrated in Figure 1. To investigate the impact of intermolecular interaction on real materials, packing models of 1, Ph1, 2, and Ph2, that is D1, DPh1, D2-a/b, and DPh2 with the nearest intermolecular separations within 5Å , were taken from crystal structures of 4,4-difluoro-1,2,3,5,7-pentamethyl-6-ethyl-4-bora3a,4a-diaza-s-indacene, 4,4-difluoro-1,7-dimethyl-2,3,6-terethyl-8-(4-tolyl)-4-bora-3a,4a-diaza-s-indacene, and bis(4,4-difluoro-1,7-dimethyl-2,3, 6-terethyl-8-(4-tolyl)-4-bora-3a,4a-diaza-s-indacene) [12], respectively. Note that for model compound D2-a/b, H-atom instead of 4-tolyl was used, because the presence of 4-tolyl in 8-position has been proved having less effect on the optical properties of BODIPY [10a, 22].…”

“…Recently, Broring et al synthesized alkyl-substituted BODIPY (molecules 1 and Ph1) ( Fig. 1) and its dimeric bis-BODIPY (molecules 2 and Ph2) through a facile synthetic route [12]. Molecule bisBODIPY with folded structure containing two directly linked BODIPY chromophores can be considered as the simplest oligomer model.…”