Polar alignment of dye molecules in sectors of host lattices revealed by phase sensitive second harmonic generation and scanning pyroelectric microscopy

Origin and structure of polar domains in doped molecular crystals

“…Studies of crystal doping demonstrated that the formation of a mixed molecular crystal is determined by the structure of the dopants and the structure of surface sites at which the guest molecules bind before their occlusion into the host crystal567. According to this mechanism, the dopants are incorporated in a polar mode within the bulk of the host8910 and thus convert non-polar hosts into mixed polar crystals9111213. The dopant-induced lattice polarity of the mixed crystal originates from two sources.…”

Symmetry and the polar state of condensed molecular matter

“…Basic findings concerning a bi-polar state are experimentally well confirmed [10] for as grown crystals involving (i) channel-type inclusion compounds [11], (ii) single component molecular crystals [12], (iii) solid solutions of molecular crystals [13], (iv) dye stained inorganic host lattices [14], (v) some ionic crystals [10] and (vi) even natural tissues [15,16]. Particularly instructive are (i) channel type inclusion compounds and (ii) single component molecular crystals, nucleating both into a centric seed, but developing a bi-polar state during growth.…”

Dinitroxide biradical crystals with polar order

“…[1][2][3][4] For example, the possibility of engineering crystals in which guests are located in precise non-centrosymmetric positions [5][6][7][8][9] holds great promise for second-harmonic generation (SHG) in nonlinear optics. [10][11][12] Yet in the majority of cases, the molecules pack in the crystal to cancel their dipolar moment, often at the origin of crystallization in centrosymmetric space groups. However in some cases, it can happen that a molecule crystallizes in a noncentrosymmetric space group for some reasons that are still unclear.…”