Optical Characteristics of Hybrid Macrocycles with Dithienogermole and Tricoordinate Boron Units

Abstract

The introduction of unconventional elements into π‐conjugated systems has been studied to manipulate the electronic states and properties of compounds. Herein, boron‐ and germanium‐containing hybrid macrocycles, as a new class of element‐hybrid conjugated systems, have been synthesized. The palladium‐catalyzed Stille cross coupling of bis(bromothienyl)borane and bis(trimethylstannylthienyl)‐ or bis(trimethylstannylphenyl)‐substituted dithienogermoles as the boron‐ and germanium‐containing building blocks, respectively, produced a mixture of several macrocyclic compounds. Single‐crystal X‐ray analysis of the 2:2 coupling product revealed a planar structure with a cavity inside the macrocycle. The optical properties of the macrocyclic products indicated rather small electronic interactions between the building units. However, intramolecular photoenergy transfer from the dithienogermole unit to the boron unit was clearly observed with respect to the fluorescence spectra.

Synthesis and Structure‐Property Relationships in Regioisomeric Alternating Borane‐Terthiophene Polymers

“…In our case, cyclic tetramers and pentamers are obtained preferentially, possibly also aided by the bent shape of the dithienylborane building blocks (Figure 4b). These macrocycles resemble previously reported hexameric boracyclophanes with phenylene or fluorenylene bridges [14a,d] and related hybrid macrocycles containing boron in combination with other heteroatoms [14c,e,g,20] that were assembled in stepwise processes. They are also related to tetrameric thienylboranes, introduced by Siebert et al.…”

“…The higher molecular weight sample of PFB3T’‐B showed multiple series of peaks due to one or two additional thiophene units, which still primarily correspond to cyclic products. The formation of cyclic rather than linear conjugated polymers has been reported for Suzuki‐Miyaura polycondensation reactions with suitably shaped (kinked) monomers, [19] but has to our knowledge only rarely been observed [5l,14e,f] in Stille polymerization of thiophenes. In our case, cyclic tetramers and pentamers are obtained preferentially, possibly also aided by the bent shape of the dithienylborane building blocks (Figure 4b).…”

Synthesis, structure, and application of boron-containing macrocycles

“…10,12 Besides, compounds 30 , 31 , and 33 can achieve fluoride anion binding. 32 Interestingly, the fluoride binding with compound 33 led to increased fluorescence intensity.…”

“…Pd-catalyzed Stille coupling was employed to synthesize boron- and germanium-containing macrocycles ( 30 , 31 , and 33 ) reported by Jäkle, Ohshita, and co-workers (Scheme 10). 32 The key steps were furnished through the reactions of bis(bromothienyl)borane 28 and organo-tin reagents ( 29 / 32 ). The crystal data of 33 showed that the two bithienylene groups have syn conformations, while the others adopt anti -conformations.…”

Boron-Doped α-Oligo- and Polyfurans: Highly Luminescent Hybrid Materials, Color-Tunable through the Doping Density

“…An important recent finding in this regard was that the combination of furan rings with strongly electron-withdrawing groups substantially improves their resistance to oxidative degradation by lowering the compound’s highest occupied molecular orbital (HOMO) energy and therefore enhancing its overall stability. ,− The doping of conjugated π systems with trivalent boron atoms has emerged as an effective strategy to produce novel compounds with intriguing properties and functions. − …”