Conformational Editing Drives Covalent Hybridization for Nonlinear Optical Crystals.

Area of Science:

• Materials Science
• Crystallography
• Organic Chemistry

Background:

• Steric repulsion between planar organic molecules and inorganic tetrahedra limits the formation of crystalline solids.
• Organic moieties typically adopt trans-conformations, hindering close approach and covalent bond formation, often resulting in centrosymmetric structures.

Purpose of the Study:

• To develop a synthetic strategy to overcome steric constraints in organic-inorganic hybrid crystal formation.
• To create novel non-centrosymmetric hybrid materials with desirable optical properties.

Main Methods:

• A solvent-driven conformational editing strategy was employed, modulating HBF4 concentration to switch biuret from trans- to cis-conformer.
• In situ conformational switching was validated using interacting region indicator analysis and Raman spectroscopy.
• The synthesis of a novel biuret-[BO2F2] hybrid crystal and 14 additional compounds was achieved.

Main Results:

• The strategy successfully reprogrammed biuret's conformation, enabling previously inaccessible covalent bond formations.
• A new non-centrosymmetric hybrid crystal, [C2O2N3H5BF2][BF4], featuring a covalently linked biuret-[BO2F2] unit, was synthesized.
• The synthesized compound exhibits excellent properties for short-wavelength ultraviolet nonlinear optical applications.

Conclusions:

• Solvent-mediated conformational control is a viable synthetic paradigm for overcoming steric hindrance in materials synthesis.
• Biuret serves as a versatile platform for constructing diverse organic-inorganic hybrid architectures.
• This approach opens pathways to novel materials with tailored optical functionalities.