a All the geometries for the ground and excited states
were derived at the SOS-MP2 and SOS-CIS(D0) level of
theories, respectively, using aug-cc-pVDZ (aDZ) basis sets.b PT2 denotes the second order perturbation theory
calculation, i.e. , SOS-MP2 for the ground state and
SOS-CIS(D0) for the excited states; gDZ, aDZ and aTZ
stand for 6-31+G(d), aug-cc-pVDZ and aug-cc-pVTZ basis sets,
respectively. c CC represents the coupled cluster
calculation, i.e. , CCSD and EOM-CCSD for the ground and excited
states, respectively; the values are obtained via E(PT2/aDZ) +
[E(CC/gDZ) –E(PT2/gDZ)]. d Ref.[8]
Let us begin our discussion with the stabilities of ground-state dimers.
The energetic data including the binding energies, BEgs,
are listed in Table 2. As discussed above, the Stg dimer is still
found to be the most stable; its
BEgsCP value is calculated to be ca.
0.37 eV, while those of the syn and anti dimers are to be
ca. 0.09 and 0.25 eV, respectively. BSSE uncorrected values,
BEgs, also draw the same picture: ca. 1.03, 0.84, and
0.55 eV for the Stg , anti , and syn dimers,
respectively. This means that the geometry relaxation effect is not
significant enough to change the stability ordering of Cz dimers.
Consequently, these results are consistent with the picture from the
calculated PESs in Figure 2, demonstrating that the Cz dimer in the
ground state is most likely in the Stg conformation, and that in
the syn conformation is computed to be least stable. We also
note, however, that the difference in BEgs among these
conformers are somewhat modified, indicating that the structural
relaxations depend on the dimer conformation. For example, the
calculated differences in BEgs between the Stgand syn dimers are ca. 0.32 and 0.48 eV without and with geometry
relaxation, respectively, implying the larger relaxation for theStgdimer.[38]
Table 2. Calculated binding energies, their intermolecular interaction
energy components, and interplanar distance of carbazole dimers at their
ground-state geometriesa