title: 8-Amino-BODIPYs: structural variation, solvent-dependent emission, and VT NMR spectroscopic properties of 8-R2N-BODIPY.
abstract: New 8-NR2-BODIPYs, R2 = H(i)Pr (3a), H(i)Bu (3b), and Et2 (4), are reported. Restricted rotation about the C8-N bond in such molecules has been observed for the first time (3a and 3b) and evaluated using VT NMR. The fluorophores 3a and 3b are blue emitters, and the efficiency of the emission is closely related to the polarity of the solvent, e.g., hexane > toluene > DCM > THF > MeOH > H2O, an effect also noted by emission variation in alcohol solvents H(CH2)nOH, n = 1-6. In mixed-solvent systems, addition of 10-15% of the more polar solvent results in transformation of the emission properties to those of the bulk polar solvent. Compound 4 has zero emission in all solvents. The crystal structures of 3a, 3b, and 4 are reported, along with that of the parent 8-NH2-BODIPY (2). Compounds 2, 3a, and 3b exhibit trigonal planar N atoms which are coplanar with the BODIPY core; 4 exhibits a very significant distortion that breaks the planarity of the extended BODIPY π system due to the steric impact of the two ethyl groups, an observation that explains the lack of emission for 4.
authors.affiliation: Department of Chemistry, The University of Texas at El Paso, El Paso, Texas 79968-0513, United States.
authors.forename: Robinson I
authors.initials: RI
authors.lastname: Roacho
authors.forename: Alejandro
authors.initials: A
authors.lastname: Metta-Magaña
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Portillo
authors.forename: Eduardo
authors.initials: E
authors.lastname: Peña-Cabrera
authors.forename: Keith H
authors.initials: KH
authors.lastname: Pannell
mesh_terms: D000588:Amines / Q000138:chemical synthesis* / Q000737:chemistry; D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012997:Solvents / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D000588:Amines; D001896:Boron Compounds; D005456:Fluorescent Dyes; D012997:Solvents