A facile and versatile approach was developed to access ambipolar boron-containing macrocycles. Two examples of new conjugated cyclic motifs are presented with carbazole moieties as donors and borane moieties as acceptors embedded into the ring system. They were first predicted using computational methods. Possible targets with appropriately shaped π-conjugated bridges that minimize the overall ring strain were identified and their geometry was optimized by DFT methods. The synthetic demonstration was then accomplished using organometallic condensation reactions under high dilution conditions. The resulting monodisperse macrocycles provide important insights into the design principles necessary for the preparation of new unstrained macrocycles with interesting optical and electronic characteristics. The current research also offers a more general approach to conjugated ambipolar B/N macrocycles as a promising new family of (opto)electronic materials.

Polycationic macrocycles are attractive as they display unique molecular switching capabilities arising from their redox properties. Although diverse polycationic macrocycles have been developed, those based on cationic boron systems remain very limited. We present herein the development of novel polycationic macrocycles by introducing organoboronium moieties into a conjugated organoboron macrocyclic framework. These macrocycles consist of four bipyridylboronium units that are connected by fluorene and either electron-deficient arylborane or electron-rich arylamine moieties. Electrochemical studies reveal that the macrocycles undergo reversible multi-step redox processes with transfer of up to 10 electrons. Switchable electrochromic behavior is demonstrated via spectroelectrochemical studies and the observed color changes are rationalized by correlation with computed electronic transitions using DFT methods.Endowed with unique electrooptical characteristics, conjugated polycations serve as important components in the fields of supramolecular materials and redox-responsive systems. [1] Among them, polycationic macrocycles such as Stoddarts "blue box" [2] generate impressive interlocked structures and exhibit unique molecular switching capabilities. [3] Since their first discovery, numerous derivatives have been synthesized and utilized in supramolecular assemblies, host-guest chemistry, [4] molecular electronics, [5] electron transfer, [6] and electrochromic [7] materials. Although diverse polycationic macrocycles have been reported, [8] those based on cationic boronium moieties remain very limited. [9] Very recently, coordination-driven self-assembly to build up polycationic boron macrocycles was reported by Himmel and co-workers. [9c] These macrocycles are composed of cationic diborane units that are linked together by pyrazine, 4,4'-bipyridine, or 1,2di(4-pyridyl)ethene.Over the course of our studies on organoboron pconjugated materials, [10] we developed a unique class of boracyclophanes with strongly Lewis acidic boron sites, including ambipolar borazine A [11] with its alternating electron-deficient arylboranes and electron-rich arylamines and the highly electron-deficient macrocycles B [12] (Figure 1 a). [13]

We introduce an ew boron-doped cyclophane,t he hexabora[1 6 ]cyclophane B6-F Mes,i nw hich six tricoordinate borane moieties alternate with short conjugated p-phenylene linkers.E xocyclic 2,4,6-tris(trifluoromethyl)phenyl ( F Mes) groups serve not only to further withdraw electron density but at the same time sterically shield the boron atoms,resulting in am acrocycle that is both highly electron-deficient and stable.The optical and electronic properties are compared with those of related linear oligomers and the electronic structure is further evaluated by computational methods.T he studies uncover unique properties of B6-F Mes,i ncluding al ow-lying and extensively delocalized LUMO and aw ide HOMO-LUMO gap,w hicha rise from the combination of ac yclic psystem, strong electronic communication between the closely spaced borons,a nd the attachment of electron-deficient pendent groups.T he binding of small anions to the electrondeficient macrocycle and molecular model compounds is investigated and emissive exciplexes are detected in aromatic solvents.

Donor−π−acceptor compounds based on arylamine and arylborane moieties connected by a π-conjugated linker are attractive materials in organic electronics and imaging applications due to the strong charge transfer character that leads to low energy absorption and solvatochromic emission properties. Here we introduce a new conjugated macrocyclic system that consists of four arylborane and two arylamine units as confirmed by singlecrystal X-ray structure analysis. The acceptor character of the arylboranes is enhanced by exocyclic electron-withdrawing 2,4,6tris(trifluoromethyl)phenyl ( F Mes) substituent as well as the mutual interaction between adjacent boranes. The absorption, solventdependent emission, and electrochemical properties are studied and compared to those of other macrocyclic organoboranes. Computational studies offer additional insights into the electronic structure. Due to the enhanced acceptor character of the boranes, the LUMO orbitals are lower lying, leading to more facile reduction, red-shifted absorption and emission, and larger Stokes shifts than those found for previously studied B−N macrocycles.

We introduce a new boron‐doped cyclophane, the hexabora[16]cyclophane B6‐FMes, in which six tricoordinate borane moieties alternate with short conjugated p‐phenylene linkers. Exocyclic 2,4,6‐tris(trifluoromethyl)phenyl (FMes) groups serve not only to further withdraw electron density but at the same time sterically shield the boron atoms, resulting in a macrocycle that is both highly electron‐deficient and stable. The optical and electronic properties are compared with those of related linear oligomers and the electronic structure is further evaluated by computational methods. The studies uncover unique properties of B6‐FMes, including a low‐lying and extensively delocalized LUMO and a wide HOMO–LUMO gap, which arise from the combination of a cyclic π‐system, strong electronic communication between the closely spaced borons, and the attachment of electron‐deficient pendent groups. The binding of small anions to the electron‐deficient macrocycle and molecular model compounds is investigated and emissive exciplexes are detected in aromatic solvents.