Triangular Expanded Hemiporphyrazines: Electronic Structures and Nanoscale Characterization of Their Adlayers on Au(111)

Abstract

Electronic structures and direct observation of adlayers on Au(111) of triangular expanded hemiporphyrazines that can be classified into azaporphyrinoids and which can trap three transition metal ions are reported. The electronic structure was examined by electronic absorption and magnetic circular dichroism (MCD) spectroscopies and interpreted in conjunction with molecular orbital (MO) calculations. Both metal-free and metallated compounds were 30 π-electron systems with n = 7 in 4n + 2 aromaticity. In addition, calculations of the anisotropy of the induced current density (ACID) and nucleus-independent chemical shift (NICS) were performed. The inner core region of the metal-free compound was weakly anti-aromatic or nonaromatic, but after metal insertion, this region increased aromatic character. The direct observation of adlayers of one of their cobalt and nickel complexes on Au(111) by scanning tunneling microscopy (STM) revealed that these three ions are arranged specifically in the shape of a triangle.

Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear MII3O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet–Quartet Transitions in the Dianions

“…The nonaromatic character of H 3 Hhp was the subject of a number of the articles. ,, Recently, the appearance of the aromatic character of the macrocycles at complex formation of some substituted Hhps has been described . The NICS values (fragments a 1 –f 3 , Figure S13) are negative for all local fragments of the {Ni 3 O­(Hhp)} 2– and {Cu 3 O­(Hhp)} 2– dianions (from approximately −2.2 to −13.4 ppm, Table S2), indicating their aromatic character.…”

Phenanthroline-Fused Phthalocyanine Analogues Having a Monovalent Corrole Inner Perimeter and 4nπ Nonaromatic Properties

“…For 3Ni (Figure B), the NICS values changed to nearly zero (in the central region) or negative (in the phenanthroline region), indicating that insertion of a Ni center significantly increased the diatropic aromatic character. A similar metal effect has been reported recently . To visualize the flow of charge, anisotropy of the current-induced density (ACID) calculations were also performed for 3Ni .…”

“…A similar metal effect has been reported recently. 10 To visualize the flow of charge, anisotropy of the current-induced density (ACID) calculations were also performed for 3Ni. 11 As shown in Figure 1E, a clockwise flow of charge is seen in the two benzene and phenanthroline rings, while an anticlockwise flow appears in the two pyrrole rings and the flow is very weak in the core.…”

Complexes of Ca(II), Ni(II) and Zn(II) with Hemi- and Dicarbahemiporphyrazines: Molecular Structure and Features of Metal-Ligand Bonding

“…It should be noted that the oppositely placed benzene moieties in dchp complexes with Ca and Zn are less aromatic as compared to benzene. In the very recent study [50] insertion of a metal atom into macrocyclic core was found to increase aromatic properties as compared to a free-base macrocycle. However the complexes of H 2 hp and H 2 dchp with Ca(II), Ni(II) and Zn(II) do not exhibit an unambiguous trend (Table 4).…”