Roles of Precursor Conformation and Adatoms in Ullmann Coupling: An Inverted Porphyrin on Cu(111)

Autor(es)

Moreno-Lopez, Juan Carlos ^{[1, 2]} ; John Mowbray, Duncan ^{[2, 3, 4]} ; Perez Paz, Alejandro ^{[2, 3, 4]} ; de Campos Ferreira, Rodrigo Cezar ^[5] ; dos Santos, Alisson Ceccatto ^[5] ; Ayala, Paola ^{[1, 2]} ; de Siervo, Abner ^[5]

Afiliação do(s) autor(es)

^[1] Univ Vienna, Fac Phys, A-1090 Vienna - Austria

^[2] Yachay Tech Univ, Sch Phys Sci & Nanotechnol, Urcuqui 100119 - Ecuador

^[3] Univ Basque Country, UPV EHU, Nanobio Spect Grp, E-20018 San Sebastian - Spain

^[4] Univ Basque Country, UPV EHU, Dept Fis Mat, ETSF Sci Dev Ctr, E-20018 San Sebastian - Spain

^[5] Univ Estadual Campinas, UNICAMP, Inst Fis Gleb Wataghin, BR-13083859 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: CHEMISTRY OF MATERIALS; v. 31, n. 8, p. 3009-3017, APR 23 2019.
• Citações Web of Science: 0

Resumo

Surface diffusion, molecular conformation, and on-surface coupling reactions are key processes for building tailored molecular nanostructures such as graphene nanoribbons, polycyclic aromatic hydrocarbons, and one-dimensional/two-dimensional (2D) polymers. Here, we study the surface diffusion and coupling in situ of a chlorinated porphyrin, namely 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (Cl4TPP), using a combined scanning tunneling microscopy (STM), density functional theory (DFT), and X-ray photoelectron spectroscopy approach. Using STM, we obtain surface migration and rotation barriers Delta E of 0.77 +/- 0.09 and 0.93 +/- 0.28 eV, respectively, indicative of covalent binding to the surface. In fact, we find that the precursors as well as all the reaction species exclusively (approximate to 100%) adopt a peculiar ``inverted{''} conformation covalently bonded to Cu(111). Using DFT, we have mapped two coupling reaction pathways: direct dechlorination and Cu adatom-mediated Ullmann coupling. We find that the latter is essentially barrierless, whereas the former faces a barrier of about 0.9 eV for inverted Cl4TPP on Cu(111). Our STM measurements show that C-Cu-C organometallic species are the main final products in the presence of Cu adatoms, which is explained by our DFT reaction profile when heat dissipation to the substrate is taken into account. This work not only highlights the relevance of surface adatoms in selecting the reaction pathway but also opens the possibility of precisely tailoring 2D molecular assemblies by controlling the supply of Cu adatoms. (AU)

• Processo FAPESP: 17/08846-7 - Determinação de parâmetros termodinâmicos na difusão e formação de nanomembranas de tetra-4-clorofenilporfirina em Cu(111)
• Beneficiário: Alisson Ceccatto dos Santos
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica
• Processo FAPESP: 07/54829-5 - Estrutura eletrônica e geométrica de nano materiais: um estudo por radiação sincroton
• Beneficiário: Richard Landers
• Modalidade de apoio: Auxílio à Pesquisa - Temático