Effective and fast algorithms for calculating rate constants for internal conversion (IC) and intersystem crossing (ISC) in the Franck–Condon and Herzberg–Teller approximations have been developed and implemented.

The recently synthesized cyclo[18]carbon molecule has been characterized in a number of studies by calculating electronic, spectroscopic, and mechanical properties. However, cyclo[18]carbon is only one member of the class of cyclo[ n ]carbons—standalone carbon allotrope representatives. Many of the larger members of this class of molecules have not been thoroughly investigated. In this work, we calculate the magnetically induced current density of cyclo[ n ]carbons in order to elucidate how electron delocalization and aromatic properties change with the size of the molecular ring ( n ), where n is an even number between 6 and 100. We find that the Hückel rules for aromaticity (4 k + 2) and antiaromaticity (4 k ) become degenerate for large C n rings ( n > 50), which can be understood as a transition from a delocalized electronic structure to a nonaromatic structure with localized current density fluxes in the triple bonds. Actually, the calculations suggest that cyclo[ n ]carbons with n > 50 are nonaromatic cyclic polyalkynes. The influence of the amount of nonlocal exchange and the asymptotic behavior of the exchange–correlation potential of the employed density functionals on the strength of the magnetically induced ring current and the aromatic character of the large cyclo[ n ]carbons is also discussed.

A new method for calculating internal conversion rate constants (kIC), including the anharmonic effects, and using the lagrangian multiplier technique, is proposed. The deuteration effect on kIC was investigated for...

A novel method for calculating rate constants for internal conversion (kIC) that simultaneously accounts for Duschinsky, anharmonic and Herzberg–Teller effects has been developed and implemented.

Magnetizabilities and magnetically induced current densities have been calculated and analyzed for a series of antiaromatic cyclo[4k]carbons (k=2-11), iso [n]phlorins (n=4-8), expanded porphyrinoids and meso-meso, β-β, β-β triple linked porphyrin and isophlorin arrays. The cyclo[4k]carbons with k=2-6 are predicted to be closed-shell paramagnetic molecules due to the very strong paratropic ring current combined with its large radius.Larger cyclo[4k]carbons with k=6-11 are diamagnetic, because they sustain a paratropic ring current whose strength is weaker than -20 nA T -1 , which seems to be the lower threshold value for closed-shell paramagnetism. This holds not only for cyclo[4k]carbons, but also for other organic molecules like expanded porphyrinoids and oligomers of porphyrinoids.The present study shows that meso-meso, β-β, β-β triple linked linear porphyrin and isophlorin arrays have a domain-like distribution of alternating diatropic and paratropic ring currents. The strength of their local paratropic ring currents is weaker than -20 nA T -1 in each domain. Therefore, linear porphyrin and isophlorin arrays become more diamagnetic with increasing length of the ribbon. For the same reason, square-shaped meso-meso, β-β, β-β triple linked free-base porphyrin and isophlorin tetramers as well as Zn(II) complex of the porphyrin tetramer are diamagnetic. We show that closed-shell molecules with large positive magnetizabilities can be designed by following the principle that a strong paratropic current ring combined with a large ring-current radius leads to closed-shell paramagnetism.of the ring current. The largest member of the series namely iso[8]phlorin has a magnetizability of 3532 a.u., because it sustains a very strong ring current of -617 nA T -1 whose radius is 5.3 Å. Calculations on expanded porphyrins fulfilling Hückel's rule for antiaromaticity show that orangarin, rosarin, amethyrin are diamagnetic, since they sustain paratropic ring currents that a weaker than -20 nA T -1 . The largest member of that series is the hypothetic circle-shaped [40]octaphyrin(1.1.1.1.1.1.1.1) that sustains a strong paratropic ring current of -561 nA T -1 whose radius is 5.3 Å. The circle-shaped [40]octaphyrin(1.1.1.1.1.1.1.1) molecule is therefore strongly paramagnetic with a magnetizability of 3244 a.u.

A fast method for estimating nonadiabatic coupling matrix elements (NACME) and rate constants for internal conversion (kIC) is presented. The method based on Plotnikov’s theory requires only calculations of the...

Magnetically induced ring current are calculated from the magnetic shielding tensor by employing the Ampére-Maxwell law. The feasibility of the method is demonstrated by integrating the zz component of the...

Substitution with gold(i)-containing moieties results in non-vanishing oscillator strengths and spin–orbit coupling leading to fast intersystem crossing in light-emitting heptazine derivates with an inverted singlet–triplet gap.