Orbital Interactions through Space and through Bonds

V-Shaped Tröger Oligothiophenes Boost Triplet Formation by CT Mediation and Symmetry Breaking

“…In parallel to their preparation, a comprehensive understanding of the photophysical processes making them suitable for photonics is mandatory for their successful development. In recent years, we have been exploring a variety of conjugation strategies to modulate the electronic properties of π-molecules, such as through-space interactions, 6 spiroconjugation, 7 and hyperconjugation, 8 in order to fine-tune the coupling between excited states produced by the assembly of two or more chromophores.…”

“…Going to particular examples of the previously mentioned electronic effects, the DBCO fragment (i.e., a in Scheme 1 or 1,4-diazabicyclo[2.2.2]octane) represents a typical case with through-bond coupling or interaction (TBI) between the lone electron pairs of the nitrogens (n) assisted by the antibonding sigma orbitals (σ*) of the bismethylene bridge (n/σ* TBI and orbital structure in Scheme 1 ). 9 Another example is fragment b in Scheme 1 , i.e., DBCO with the two nitrogen atoms replaced by vinylenes, where through-space interaction (TSI) occurs between the π orbitals of the two double bonds (π/π* TSI and orbital structure in Scheme 1 ). 9 Finally, in the diazocine (DA) ring in Scheme 1 , the interactions can be considered as a mixture of those in fragments a and b (i.e., n/π* and n/σ* TBI between the nitrogens and the vinylenes, n/σ* TBI between the nitrogens, and π/π* TSI between the vinylenes).…”

“… 9 Another example is fragment b in Scheme 1 , i.e., DBCO with the two nitrogen atoms replaced by vinylenes, where through-space interaction (TSI) occurs between the π orbitals of the two double bonds (π/π* TSI and orbital structure in Scheme 1 ). 9 Finally, in the diazocine (DA) ring in Scheme 1 , the interactions can be considered as a mixture of those in fragments a and b (i.e., n/π* and n/σ* TBI between the nitrogens and the vinylenes, n/σ* TBI between the nitrogens, and π/π* TSI between the vinylenes). Extending the DA unit by fusing a benzene ring at each vinylene results in the so-called Tröger’s base ( Scheme 1 ).…”

The Role of Hyperconjugation on the Structure and C–H Stretching Frequencies of 3,3′-Ethane-1,2-diyl- bis-1,3,5-triazabicyclo[3.2.1]octane (ETABOC): An X-Ray Structure and Vibrational Study

“…Additionally, it is well known that for diazabicycloalkanes and other polycyclic systems, the lone pair-lone pair interactions, either through space and/or sigma bonds, play an important role in stabilizing these polyamines, including their protonated or radical cation forms [6][7][8][9][10][11][12][13]. Moreover, such interactions depend on the spatial orientation of the lone pairs [12,13].…”