Controlled hierarchical self-assembly of hyperbolic paraboloid molecules into two-dimensional superstructures with second-harmonic generation characteristic.

Abstract

Hyperbolic paraboloid molecules, as systems with remarkable negative Gaussian curvature, have garnered considerable attention in chemistry and materials science due to their unique physicochemical properties. However, controlled organization of these curvature building blocks into well-defined superstructures remains challenging, primarily attributed to the constraints of their inherently contorted structures. Herein, we report the successful formation of hyperbolic-paraboloid-based crystalline two-dimensional (2D) superstructures in a controlled hierarchical manner. Employing a rigid yet flexible molecular design strategy, we guide the hyperbolic-paraboloid molecules through hierarchical self-assembly method from dimers to one-dimensional (1D) supramolecular columns and ultimately to 2D superstructures. Remarkably, these 2D superstructures exhibit strong second harmonic generation (SHG) with excellent polarization dependence. The strongest SHG signals were recorded at 1.5 × 10⁵ for 2D HPS-MT and 1.1 × 10⁵ for 2D HPS-Z, with polarization dependence of the SHG responses reaching 87.5% for 2D HPS-MT and 81% for 2D HPS-Z.