title: Boron complexes of aromatic ring fused iminopyrrolyl ligands: synthesis, structure, and luminescence properties.
abstract: The condensation reactions of 2-formylindole (1) or 2-formylphenanthro[9,10-c]pyrrole (2) with various aromatic amines afforded the corresponding phenyl or phenanthrene ring fused mono-/bis-iminopyrrole ligand precursors 3-8, which, upon reaction with BPh3in an appropriate molar ratio, led to the new mono- and diboron chelate compounds Ph2B[NC8H5C(H)[double bond, length as m-dash]N-2,6-Ar] (Ar = 2,6-iPr2C6H39; C6H510), Ph2B[(NC8H5C(H)[double bond, length as m-dash]N)2-1,4-C6H4]BPh211, Ph2B(NC16H9C(H)[double bond, length as m-dash]N-Ar) (Ar = 2,6-iPr2C6H312; C6H513), and Ph2B[(NC16H9C(H)[double bond, length as m-dash]N)2-1,4-C6H4]BPh214, respectively. Boron complexes 12-14, containing a phenanthrene fragment fused to the pyrrolyl C3-C4 bond, are highly fluorescent in solution, with quantum efficiencies of 37%, 61% and 58% (in THF), respectively, their emission colours ranging from blue to orange depending on the extension of π-conjugation. Complexes 9-11, containing a benzene fragment fused to the pyrrolyl C4-C5 bond, are much weaker emitters, exhibiting quantum efficiencies of 10%, 7% and 6%, respectively. DFT and TDDFT calculations showed that 2,6-iPr2C6H3N-substituents or, to a smaller extent, the indolyl group prevent a planar geometry of the ligand in the excited state and reveal the existence of a low energy weak band in all the indolyl complexes, which is responsible for the different optical properties. Non-doped single-layer light-emitting diodes (OLEDs) were fabricated with complexes 9-14, deposited by spin coating, that of complex 13 revealing a maximum luminance of 198 cd m-2.
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt and School of Chemical and Biotechnology, SASTRA University, Thanjavur-613 401, India.
authors.forename: D
authors.initials: D
authors.lastname: Suresh
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: Bruno
authors.initials: B
authors.lastname: Ferreira
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: Patrícia S
authors.initials: PS
authors.lastname: Lopes
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: Clara S B
authors.initials: CS
authors.lastname: Gomes
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: Paramasivam
authors.initials: P
authors.lastname: Krishnamoorthy
authors.affiliation: Instituto de Telecomunicações, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Charas
authors.affiliation: Centro de Química e Bioquímica, DQB, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal.
authors.forename: Diogo
authors.initials: D
authors.lastname: Vila-Viçosa
authors.affiliation: Instituto de Telecomunicações, Av. Rovisco Pais, 1049-001 Lisboa, Portugal and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: Jorge
authors.initials: J
authors.lastname: Morgado
authors.affiliation: Centro de Química e Bioquímica, DQB, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal.
authors.forename: Maria José
authors.initials: MJ
authors.lastname: Calhorda
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: António L
authors.initials: AL
authors.lastname: Maçanita
authors.affiliation: Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. pedro.t.gomes@tecnico.ulisboa.pt.
authors.forename: Pedro T
authors.initials: PT
authors.lastname: Gomes