title: UV-photoelectron spectroscopy of BN indoles: experimental and computational electronic structure analysis.
abstract: We present a comprehensive electronic structure analysis of two BN isosteres of indole using a combined UV-photoelectron spectroscopy (UV-PES)/computational chemistry approach. Gas-phase He I photoelectron spectra of external BN indole I and fused BN indole II have been recorded, assessed by density functional theory calculations, and compared with natural indole. The first ionization energies of these indoles are natural indole (7.9 eV), external BN indole I (7.9 eV), and fused BN indole II (8.05 eV). The computationally determined molecular dipole moments are in the order: natural indole (2.177 D) > fused BN indole II (1.512 D) > external BN indole I (0.543 D). The λmax in the UV-vis absorption spectra are in the order: fused BN indole II (292 nm) > external BN indole I (282 nm) > natural indole (270 nm). The observed relative electrophilic aromatic substitution reactivity of the investigated indoles with dimethyliminium chloride as the electrophile is as follows: fused BN indole II > natural indole > external BN indole I, and this trend correlates with the π-orbital coefficient at the 3-position. Nucleus-independent chemical shifts calculations show that the introduction of boron into an aromatic 6π-electron system leads to a reduction in aromaticity, presumably due to a stronger bond localization. Trends and conclusions from BN isosteres of simple monocyclic aromatic systems such as benzene and toluene are not necessarily translated to the bicyclic indole core. Thus, electronic structure consequences resulting from BN/CC isosterism will need to be evaluated individually from system to system.
authors.affiliation: Department of Chemistry, Boston College , Chestnut Hill, Massachusetts 02467, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Chrostowska
authors.forename: Senmiao
authors.initials: S
authors.lastname: Xu
authors.forename: Audrey
authors.initials: A
authors.lastname: Mazière
authors.forename: Katherine
authors.initials: K
authors.lastname: Boknevitz
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Eric R
authors.initials: ER
authors.lastname: Abbey
authors.forename: Alain
authors.initials: A
authors.lastname: Dargelos
authors.forename: Alain
authors.initials: A
authors.lastname: Graciaa
authors.forename: Shih-Yuan
authors.initials: SY
authors.lastname: Liu
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D004583:Electrons; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D056951:Photoelectron Spectroscopy; D011789:Quantum Theory; D013237:Stereoisomerism; D014466:Ultraviolet Rays
chemical_list: D001896:Boron Compounds; D007211:Indoles; C030374:indole
references.citation: J Biol Rhythms. 2005 Aug;20(4):291-303
references.pmid: 16077149
references.citation: J Chem Phys. 2007 Apr 14;126(14):144105
references.pmid: 17444699
references.citation: Angew Chem Int Ed Engl. 2006 Oct 13;45(40):6723-5
references.pmid: 16983713
references.citation: Org Biomol Chem. 2013 Apr 7;11(13):2060-9
references.pmid: 23403937
references.citation: J Med Chem. 2007 Apr 19;50(8):1727-30
references.pmid: 17361995
references.citation: Chem Rev. 1998 Apr 2;98(2):705-762
references.pmid: 11848913
references.citation: J Am Chem Soc. 2012 Jun 20;134(24):10279-85
references.pmid: 22616808
references.citation: J Am Chem Soc. 2008 Nov 26;130(47):16069-79
references.pmid: 18980311
references.citation: Psychopharmacology (Berl). 2001 Apr;155(1):1-10
references.pmid: 11374326
references.citation: Phys Rev A Gen Phys. 1988 Sep 15;38(6):3098-3100
references.pmid: 9900728
references.citation: Biochem J. 1992 Sep 1;286 ( Pt 2):491-5
references.pmid: 1530581
references.citation: Angew Chem Int Ed Engl. 2012 Jun 18;51(25):6074-92
references.pmid: 22644658
references.citation: Tetrahedron. 2011 Sep 23;67(38):7195-7210
references.pmid: 25484459
references.citation: Org Lett. 2010 Aug 6;12(15):3386-9
references.pmid: 20586441
references.citation: Chem Biol. 2007 Jun;14(6):659-69
references.pmid: 17584613
references.citation: Angew Chem Int Ed Engl. 2008;47(2):242-4
references.pmid: 18000932
references.citation: J Am Chem Soc. 2010 Nov 24;132(46):16340-2
references.pmid: 21043508
references.citation: Methods Enzymol. 1997;278:113-50
references.pmid: 9170312
references.citation: Chem Rev. 2005 Oct;105(10):3842-88
references.pmid: 16218569
references.citation: Angew Chem Int Ed Engl. 2009;48(37):6817-9
references.pmid: 19688806
references.citation: Angew Chem Int Ed Engl. 2002 Nov 4;41(21):4066-9
references.pmid: 12412083
references.citation: Phys Rev B Condens Matter. 1988 Jan 15;37(2):785-789
references.pmid: 9944570
references.citation: Dalton Trans. 2009 Feb 28;(8):1339-51
references.pmid: 19462655
references.citation: Chemistry. 2013 Oct 25;19(44):14983-8
references.pmid: 24108670
references.citation: Science. 1985 Jul 5;229(4708):23-8
references.pmid: 3892686
references.citation: Angew Chem Int Ed Engl. 2013 Feb 25;52(9):2599-601
references.pmid: 23355270
references.citation: J Org Chem. 2008 May 16;73(10):3667-73
references.pmid: 18412391
references.citation: J Phys Chem A. 2012 Sep 20;116(37):9315-20
references.pmid: 22934652
references.citation: J Chem Phys. 2009 May 21;130(19):194114
references.pmid: 19466828
references.citation: J Nutr. 2007 Jun;137(6 Suppl 1):1504S-1508S; discussion 1516S-1517S
references.pmid: 17513416
references.citation: Proc Natl Acad Sci U S A. 2002 Mar 5;99(5):2772-7
references.pmid: 11880629
references.citation: Chemphyschem. 2012 Jan 16;13(1):226-36
references.pmid: 22174079
references.citation: Chem Commun (Camb). 2010 May 28;46(20):3604-6
references.pmid: 20383396
references.citation: J Am Chem Soc. 2011 Aug 3;133(30):11508-11
references.pmid: 21751771
references.citation: J Phys Chem A. 2005 Sep 22;109(37):8348-55
references.pmid: 16834226
references.citation: Nat Prod Rep. 2006 Aug;23(4):532-47
references.pmid: 16874388
references.citation: Life Sci. 2005 Dec 22;78(5):442-53
references.pmid: 16236327
references.citation: J Am Chem Soc. 2009 Jul 8;131(26):9201-3
references.pmid: 19522499
references.citation: Nature. 2007 Apr 5;446(7136):640-5
references.pmid: 17410169
references.citation: Dalton Trans. 2009 Apr 21;(15):2823-31
references.pmid: 19333506