Organoboron Complexes in Edge‐Sharing Macrocycles: The Triphyrin(2.1.1)–Tetraphyrin(1.1.1.1) Hybrid

Abstract

The formation of a precisely designed environment predefined for stabilizing electron‐deficient atoms, such as boron(III), is an important approach for optimizing the properties of a chromophore. A triphyrin(2.1.1) motif built on the extended π‐system of a tetraphyrin(1.1.1.1) skeleton creates a new coordination environment, with a CNN set of donors confined in a limited space predefined for binding small cations. The entrapment of boron(III) in the triphyrin(2.1.1) sector, with formation of a direct B−C bond, significantly changes the optical response and the global aromatic character of the compound, leading to an extension of the π‐delocalisation.

Multiple Coordination in Porphyrinoid Hybrid: Changing the Delocalization within the Extended π-System

“…The formed complex 18 drastically changes 1 H chemical shifts with a strong downfield relocation of the perimeter resonances what suggests a forced full planarization preferring 26 delocalization, but also a presence of both crucial for tuning the photophysical properties interaction with electron-deficient element, B-C and B-N, formed within the final molecule (Figure 4). 18 In fact the 26 electron delocalization path, a characteristic feature of a hexaphyrin(1.1.1.1.1.1) dominates in typical construction of this expanded macrocycle. Nevertheless, the extended conjugation M. Pawlicki…”

“…17 Following those observations very recently we have reported an approach (Scheme 3) leading to precise forma-tion of a structure with two coordination centers sensitive for fundamental initiators (deprotonation or coordination) drastically modifying the optic response caused by the controlled extending of delocalization. 18 In our approach we have started from the idea that a crucial factor for a planned incorporation of specific modification, i.e. doping with electron-deficient B(III), can be realized on the basis of utilization of triphyrin(2.1.1) skeleton which can be observed as a free base and has been documented as able to accommodate boron(III).…”

Multi‐Cation Coordination in Porphyrinoids

“…Much more evident extension of delocalization was achieved by Pawlicki and co‐workers for 30 —a molecule merging a tetraphyrin(1.1.1.1) ( porphyrin ) and triphyrin(2.1.1) motifs . Formation of the final product required an intramolecular McMurry coupling of 29 (Scheme ).…”

“…Upon binding fluoride to the boron center, a subtle change in chemical shift of triphyrynic protons towards the lower frequency region was observed, which is consistent with loss of planarity within this unit and therefore, less efficient orbital overlap. Therefore, the designated molecule can be described by two alternative resonance forms (Scheme ): an 18π tetraphyrin(1.1.1.1) or a 26π hexaphyrin(2.0.1.1.1.0) with a significantly increased contribution of the extended path for more planar structure …”

Edge Decoration of Anthracene Switches Global Diatropic Current That Controls the Acene Reactivity

“…The linking of two or more unsaturated hydrocarbons in one motif opens the possibility for a postsynthetic modulation of the available π-cloud that leads to changes in the character of the diatropic–paratropic couple, 1 including switching on the global delocalization. 2 The changes within π-electrons available in the system can be introduced with fundamental activators and incorporated not only in linear structures but also in macrocyclic motifs. 3 The redox activation remains a key approach for the modulation of delocalization, also introducing a global effect on the nanoscale, 4 which is responsible for the modification of the properties of structures incorporating polycyclic aromatic hydrocarbons (PAHs).…”