Abstract
We explore the behavior of the average of polarizability ( ), total first hyperpolarizability (βtotal) and average of second hyperpolarizability ( ) for single A/D (-NO2/-NH2) substituted [2.2]p-cyclophane. The geometric optimization was carried out at HF and DFT (SVWN, PBE, B3LYP, PBE0, BHHLYP and CAM-B3LYP) level, in gas phase, using the 6-31 + G(d,p) basis set. The static tensor components of and βtotal, in gas phase, were calculated using Field Finite (FF) methods with electric field intensities of E = ± 0.001 a.u. in each (x,y,z) axis direction. The substitution of A/D groups in positions 7–15 (structure 2 in Fig. 1) produced an increment in the values. Regardless of the A/D positions, the values showed not significant changes at all theory level. DFT results are overestimated up to 20%, if HF values are taken into account, being SVWN and PBE functionals those that give the main deviation. There are monotonic and progressive behaviors of βtotal for the 1–5 structure change as expected by orientation of the dipolar moment in both aromatic rings. With respect to the performance of DFT functionals, and βtotal results are significantly overestimated if HF values are taken into account. In fact, the relative percentage error of βtotal at DFT level with respect to HF ones is between 58 and 132%, being PBE functional those that give the main deviation. The close overlap of the orbitals between the rings facilitates chromophore delocalization to account for the observation of high βtotal in these compounds. Therefore, we expected that the contribution by coupling of the transition moment between first and higher excited states should be lie much higher due to phane effect than that for ring units. Open image in new window Fig. 1 a Single [2.2]p-cyclophane core molecule. b Geometric parameters of interest c Highlights for the 4, 7, 12, and 15 positions, which are substituted by (-NO2/-NH2) acceptor/donor pair
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