Conformational dynamics of bis(BF2)-2,2'-bidipyrrins revealed by through-space 13C-19F and 19F-19F couplings.
The conformation of [bis-(N,N'-difluoroboryl)]-3,3'-diethyl-4,4',8,8',9,9',10,10'-octamethyl-2,2'-bidipyrrin (1) in solution was studied by analyzing the 13C-19F and 19F-19F through-space spin-spin couplings. The 1H and 13C NMR spectra were assigned on the basis of nuclear Overhauser effect spectroscopy (NOESY), heteronuclear single-quantum correlation (HSQC), and heteronuclear multiple-bond correlation (HMBC) experiments. The 19F spectrum of 1 was compared with that of 2-ethyl-1,3,5,6,7-pentamethyl-4,4-difluoro-4-bor-3a,4a-diaza-s-indacen (2). The 19F-19F through-space spin--spin coupling in 1 was thus assigned and the coupling constant was obtained by simulating the coupling patterns. The obtained conformation of 1 was compared with those of the known complexes [bis-(N,N'-difluoroboryl)]-3,3',8,8',9,9'-hexaethyl-4,4',10,10'-tetramethyl-6,6'-(4-methylphenyl)-2,2'-bidipyrrin (3)and [bis-(N,N'-difluoroboryl)]-9,9'-diethyl-4,4',8,8',10,10'-hexamethyl-3,3'-bis(methoxycarbonylethyl)-2,2'-bidipyrrin (4). The conformational dynamics of 1, 3, and 4 was surveyed by observing the temperature dependence of the through-space coupling constants between 253 and 333 K. The 13C-19F and 19F-19F through-space spin-spin couplings thus confirm similar conformations of different BisBODIPYs in solution in contrast to earlier findings in the solid state.
Xie
X
X
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany. xie@staff.uni-marburg.de
Yuan
Y
Y
Krüger
R
R
Bröring
M
M
D001896:Boron Compounds / Q000737:chemistry*; D002247:Carbon Isotopes; D005461:Fluorine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012015:Reference Standards; D013696:Temperature; D013816:Thermodynamics
C547252:(bis-(N,N'-difluoroboryl))-3,3'-diethyl-4,4',8,8',9,9',10,10'-octamethyl-2,2'-bidipyrrin; D001896:Boron Compounds; D002247:Carbon Isotopes; D005461:Fluorine