Electronic Structure of 1,2-Dihydro[1,3,2]diazaborolo- [1,5-a]pyridine in Comparison with the Parent Isoindole
Résumé
Gas-phase He-I photoelectron spectra of N-tert-butyl-1,2-dihydro[ 1,3,2]diazaborolo[1,5-a]pyridine (3) and its thermolysis product, the parent compound 1, have been recorded and assessed by density functional theory calculations. Similarly, N-tert-butylisoindole (4) and the parent isoindole (2) were also studied. The first ionization energies of these compounds increase in the series 3 (6.75 eV) 1 (6.85 eV) 4 (6.9 eV) 2 (7.3 eV). Interestingly, the HOMOs of 1 and 3 are Introduction BN/CC isosterism has emerged as an attractive strategy for enlarging the range of compounds for fundamental research as well as materials science and with potential applications in medicine.[1] Thus, in recent years we have developed the chemistry of 1,3,2-diazaboroles A and their benzo-fused congeners, the 1,3,2-benzodiazaboroles B, which, according to the concept of isosterism, are related to pyrroles C or indoles D by the replacement of a CC by a BN fragment.[2] In addition to its rich chemistry, the benzodiazaborolyl unit has turned out to be an efficient π-electron donor in a wide variety of luminescent organic molecules.[3] In nearly [a] Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux, IPREM, UMR CNRS 5254, Université de Pau et des Pays de l'Adour, 64000 Pau, France E-mail: anna.chrostowska@univ-pau.fr http://www.univ-pau.fr/live/ [b] Fakultät für Chemie der Univerität Bielefeld, 33615 Bielefeld, Germany E-mail: lothar.weber@uni-bielefeld.de www.uni-bielefeld.de Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201301205. Eur. J. Inorg. Chem. 2013, 5672-5678 5672 © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim destabilized with respect to the first ionization energy of the isomeric 1,3,2-benzodiazaboroles (ca. 7.3 eV). The dipole moment of the ground state of isoindole derivative 4 (3.48 D) is significantly greater than that of 1,2-dihydro[1,3,2]diazaborolo[ 1,5-a]pyridine (3; 0.996 D). Upon electronic excitation, the dipole moments increased to 5.945 and 4.735 D for 4 and 3, respectively.