. Author manuscript; available in PMC: 2021 Jun 25.

Published in final edited form as: J Chem Phys. 2020 Apr 14;152(14):144307. doi: 10.1063/5.0003140

TABLE IV.

Observed and calculated rotational constants and relative energies of the s-cis and s-trans conformers of I4CA in their S₀ and S₁ electronic states. The calculated results are for planar (C_S) structures (i.e., ΔI = 0). The results for optimized C₁ structures are nearly identical.

	s-cis			s-trans
Expt.	S₀	S₁	S₁–S₀	S₀	S₁	S₁–S₀

A″/A′/Δ (MHz)	1613.2	1601.8	−11.38	1591.0	1582.7	−8.27
B″/B′/Δ (MHz)	866.6	860.4	−6.18	876.8	866.4	−10.40
C″/C′/Δ (MHz)	564.1	560.0	−4.12	565.7	560.2	−5.52

Theory	DFT^a	TD-DFT^b		DFT^a	TD-DFT^b

A″/A′/Δ (MHz)	1622.3	1595.6	−26.75	1599.7	1575.1	−24.57
B″/B′/Δ (MHz)	868.0	866.8	−1.16	878.6	874.9	−3.71
C″/C′/Δ (MHz)	565.4	561.7	−3.77	567.1	562.5	−4.65

	ΔE			ΔE		ΔE_t-c^c

Expt.(cm⁻¹)	31 122			31 505		384
Theory (cm⁻¹)^d	27 100			27 582		482

B3LYP/tzvp with empirical dispersion = gd3bj.

TD-B3LYP/tzvp with empirical dispersion = gd3bj.

Origin energy difference: s-trans–s-cis.

The calculated DFT energy difference (s-trans–s-cis) with zero-point corrections is −94 cm⁻¹.