Observing Second‐Order Nonlinear Optical Properties by Symmetry Breaking in Centrosymmetric Furan‐Containing Oligoaryl Cyclophandienes

Abstract

Centrosymmetric furan-containing cyclophandienes 3 and 4, synthesized by our furan annulation protocol, have been shown to exhibit extraordinarily large Stokes shifts and second-order nonlinear optical beta values. The beta values for 3 and 4 measured at 1.32 mum are 208 and 530x10(-30) esu, respectively. The beta values of 3 and 4 are similar to those of respective cyclophenes 1 a and 7 in which strong hyperpoarizable interactions between two twisted pi-systems (oligoaryl and bridging double bond) might take place. Symmetry breaking due to the resonance contribution (cf. 2) and the unique structural features of 3 and 4 has been used to account for this unusual photophysical behavior.

Charge-Transfer Interactions in Organic Functional Materials

“…Particularly, Bazan et al have exploited the advantage of well-defined three-dimensional structures in cyclophanes that contains [2.2]paracyclophane core and found their potential applications in designing organic nonlinear optical materials [16,17]. More recently, it has been shown that chromophores with twisted π-electron systems in a cyclophane system having five-membered hetero-aromatic rings as electron donors and a bridging double bond as electron acceptor exhibit molecular hyperpolarizability with exceptionally high μβ values [18,127]. Interestingly, quantum-chemical calculations suggest that these cyclophane architectures with one or two unsaturated bridging double bonds reveal intramolecular charge transfer characteristics in the lowest excited state [18,127].…”

“…More recently, it has been shown that chromophores with twisted π-electron systems in a cyclophane system having five-membered hetero-aromatic rings as electron donors and a bridging double bond as electron acceptor exhibit molecular hyperpolarizability with exceptionally high μβ values [18,127]. Interestingly, quantum-chemical calculations suggest that these cyclophane architectures with one or two unsaturated bridging double bonds reveal intramolecular charge transfer characteristics in the lowest excited state [18,127]. Accordingly, it is intriguing to study the nature of the excited states delocalization in detail for these bichromophoric cyclophanes with unsaturated tethers.…”

“…Incorporation of five-membered heteroaromatic rings into teraryl-cyclophane system could lead to a dihedral angle between chromophore and tether of about 40-45 degrees. We have previously synthesized the furan-containing cyclophanes containing saturated and unsaturated tethers [18,127]. Cyclophanes with double-bonded tether could have a new low energy band in the absorption spectrum but the corresponding saturated cyclophane with only single bond tether did not.…”

Design and Synthesis of Amino Acid Derivatives via Diethyl Acetadimalonate and Late‐Stage Modification by Chemical Methods

“…Once the bromo compounds 14 a and 14 b are in hand, the next step is to prepare sulfur containing amino acid derivatives by reaction with potassium thioacetate and it was reacted with bromo compounds 14 a and 14 b in the presence of potassium carbonate in methanol to produce sulphide containing amino acid derivatives in an excellent yield (Scheme 3). [33] Since, S-allyl compounds show biologically activity, we expanded the substrate scope with a wide range of benzyl bromides (Scheme 3). The treatment of allyl and propargyl bromide with potassium thioacetate delivered the unsaturated AAA derivatives 31-34, (Figure 4) in 87-91% yields.…”

A tribute to Professor Tien-Yau Luh

“…Presumably, the resonance contribution in 9 may desymmetrize the structure for 10, resulting in optical nonlinearity. 37 When R 1 is a sterically hindered tert-butyl group and R 2 is Me3Si in eq 20, reaction of the propargylic dithioacetal with BuLi followed by an aldehyde gives the carbinol 12, which is converted stereoselectively under Mitsunobu conditions into the corresponding enyne 13. 38 This transformation has been used for the iterative synthesis of Z-oligodiacetylenes 14.…”