Ethyne-Linked Push–Pull Chromophores: Implications of Crystal Structure and Molecular Electronics on the Quadric Nonlinear Activity

Abstract

Three ethyne-linked push–pull materials consisting of a dimethylaniline donor and acceptors of increasing electron-withdrawing strength were prepared as nonlinear optical chromophores. Despite a high similarity of the molecular structures, all three materials featured unrelated non-centrosymmetric crystallization behavior. One of the compounds exhibits a remarkable packing with Z′ = 16 molecules in the asymmetric unit forming two interpenetrating subsystems. Inspection of the nonlinear optical activity of single crystalline powders revealed an extraordinarily efficient second harmonic generation of one of the materials with a 1200-fold increased second harmonic response compared to potassium dihydrogen phosphate. The second harmonic generation efficiency of the materials under investigation has been related to both the intrinsic molecular properties as well as the alignment of the individual chromophores within the crystal packing, highlighting the importance of a multidisciplinary approach to understand the properties of nonlinear optical materials.

Complementary, Cooperative Ditopic Halogen Bonding and Electron Donor-Acceptor π-π Complexation in the Formation of Cocrystals

“…The single crystal X-ray structure of 1 is included in the supporting information . The structure of 2 has been published [ 23 , 24 ]. Compound 3 was prepared through Sonogashira coupling of the corresponding iodoarene and terminal alkyne as shown in Figure 3 .…”

Crystal Structures and Fluorescence Spectroscopic Properties of a Series of α,ω‐Di(4‐pyridyl)polyenes: Effect of Aggregation‐Induced Emission

“…Neutral pyridine rings are an important structural motif in the construction of molecular crystals and molecular assemblies on surfaces . The ring can serve as 1) CH⋅⋅⋅N hydrogen bond acceptor by using the lone pair of the N atom, 2) CH⋅⋅⋅N bond donor by using the sp 2 ‐CHs of the ring, and 3) π‐system in CH⋅⋅⋅π and π‐π intermolecular interactions by using the ring π‐electrons.…”

“…In the crystal structure construction of 4‐ethynylpyridine and its related compounds, CH⋅⋅⋅N bonds involving the strongly acidic sp ‐CHs play an important role . Also, there are many compounds whose structures are stabilized by CH⋅⋅⋅N hydrogen bonds with less acidic sp 2 ‐CH donors . Even very weakly acidic sp 3 ‐CHs can participate in the formation of CH⋅⋅⋅N hydrogen bonds …”

A novel selenoalkenyl-isoxazole based donor–acceptor nonlinear optical material

“…Recently, we demonstrated that the analysis of the hyperpolarizabilities of individual molecules and their actual orientation in the single crystal is a useful tool to explain macroscopic SHG efficiency of powdered crystals of organic chromophores. 20 Consequently, the static first-order hyperpolarizability tensors β ijk of both molecules were calculated using the Gaussian 09 package. The molecular geometry determined by X-ray diffraction was employed in these calculations ( Fig.…”