Optimized Cz dimers: Stg, syn, and anti conformations
Before we discuss the relative stabilities of optimized dimers, we first
briefly compared the calculation data in this study and experimental
values in the
literature,[8] for
the singlet (E(S1)) and triplet (E(T1))
excited state energies, and their difference, ΔEST, of
the Cz monomer; see Table 1. As reported
previously,[15,
36-37] the data in Table 1 clearly
show that all the methodologies in this test consistently overestimate
E(S1) and E(T1) compared to experiments;
the calculated E(S1) and E(T1) are ca.
0.38~0.49 eV and ca. 0.15~0.40 eV higher
than the experimental values, respectively. However, their energy
differences, ΔEST, are computed to be ca. 0.06 to 0.31
eV higher, meaning that the singlet and triplet excitation energy were
calculated in a reasonably balanced way. We most importantly note that
the SOS-CIS(D0)/aDZ calculation level yields the best
values compared to the experimental data in the literature; the
differences between the calculated values at this level and experimental
data are ca. 0.38, 0.32, and 0.06 eV, for the E(S1),
E(T1), and ΔEST, respectively. Thus, the
stabilities of Cz dimers are judged mainly by the energy values derived
at this level of theory.
Table 1. Adiabatic excitation energies (in eV) for the lowest-lying
singlet (S1) and triplet (T1) states,
and their difference of carbazole moleculea