Molecular electronic structure of subphthalocyanine macrocycles

Abstract

<jats:p> Quantum chemical calculations at semiempirical (MNDO methods) and ab initio (6-31G and STO-3G basis ses) levels have been performed on boron(III) subphthalocyanines 1-10. Theoretical calculations predict a cone-shaped structure for these compounds independently of the kind of peripheral substitution and even of compositional changes in the central region of the macrocycle (for example, substitution of the boron atom by two hydrogens). The theoretical calculations are in excellent agreement with previous X-ray determinations. </jats:p>

Density functional study of the redox processes in subphthalocyanines

“…Oxidation and reduction give rise to the lengthening and shortening, respectively, of the BCl bond length. A possible broad explanation for this fact is that the addition of one or more electrons increases the electron density in the macrocycle (because the redox processes in SubPc mainly involve the macrocycle but not the Cl axial substituent 19–21) and, consequently, leads to an increase of the repulsion between the Cl atom and the macrocycle that are both negatively charged. Because Δ d /Δ d and Δ d /Δ d are less than 2, it can be concluded that these repulsive effects are not additive.…”

“…This may be explained taking into account that the reductive electrons are mostly located in the macrocycle as suggested by the spatial distribution of the LUMOs (see Refs. 19–21).…”

“…Redox reactions in both porphyrins and phthalocyanines are known to take place at both the central metal (in particular when that is a transition metal) and at the conjugated macrocycle levels 18. In the case of SubPcs, it was suggested 3, 4, 19–21 that redox reactions involve the SubPc macrocycle but do not involve the central boron (which is in a saturated valence state). More recent calculations indicate that peripheral substituents on the SubPc macrocycle may also participate in the redox processes 20.…”

A Novel Route To Molecular Self-Assembly: Self-Intermixed Monolayer Phases

“…[10,16] Both approaches indicate an excess of electronic charge on the electronegative atoms which surround the electron-deficient boron. This charge is compensated by an electron deficit which is mainly localized on the six central carbon atoms (Figure 4).…”

“…results in a calculated permanent axial dipole moment of 0.95 e ä pointing away from the Cl, the magnitude of which compares well to a measured value of 1.1 e ä and to the value of 1.2 e ä predicted by AM1 calculations. [16] Each SubPc molecule is presumably bound to the substrate by a Cl ± Ag interaction and by electrostatic attraction of its polar charge distribution with the induced counter polarization of the metallic substrate. On the basis of XPS and UPS data [17] we conclude that the SubPc is adsorbed intact with the Cl pointing towards the substrate.…”