Static (hyper)polarizabilities and absorption spectra of single [2.2]p-cydophane NO_2/NH_2 substituted from DFT methods

摘要

We explore the behavior of the average of polarizability (< a >), total first hyperpolarizability (β_(total) and average of second hyperpolarizability (< y >) for single A/D (-NO_2/-NH_2) substituted [2.2]p-cyclophane. The geometric optimization was carried out at HF and DFT (SVWN, PBE, B3LYP, PBEO, BHHLYP and CAM-B3LYP) level, in gas phase, using the 6-31 + G(d,p) basis set. The static tensor components of < a > and Ptotai. 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 < a > values. Regardless of the A/D positions, the < a > values showed not significant changes at all theory level. < a > DFT results are overestimated up to 20%, if HF values are taken into account, being SVWN and PBE functional those that give the main deviation. There are monotonic and progressive behaviors of β_(total) 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, < y > and β_(total) results are significantly overestimated if HF values are taken into account. In fact, the relative percentage error of β_(tatal) 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 β_(total) 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.