New quiolinium polymorph with optimal packing for maximal off-diagonal nonlinear optical response

The influence of polymorphism on the nonlinear optical properties of HMQ-MBS (2-(4-hydroxy-3-methoxystyryl)-1-methylquinolinium 4-methoxybenzenesulfonate) crystals is investigated. By changing the solvent for crystal growth, a new polymorph has been found. While the previously reported α-phase of HMQ-MBS, having monoclinic Pc space group symmetry exhibits an optimal molecular packing for maximizing the diagonal component of the second-order nonlinear optical response, the β-phase of HMQ-MBS has monoclinic Pn space group symmetry and exhibits an optimal molecular packing for maximizing the off-diagonal response. HMQ-MBS is therefore a very interesting compound for a wide range of second-order nonlinear optical applications.

HMQ-MBS exhibits two interesting acentric polymorphs for second-order nonlinear optical applications. In one phase the chromophores pack in an optimal way to maximize the off-diagonal nonlinear susceptibility response, while in the other phase optimally to maximize the diagonal response.Figure optionsDownload as PowerPoint slide