Related Experiment Video
Updated: Jan 7, 2026
08:12
Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
Published on: September 8, 2017
10.0K
Protonation-Triggered Structural Transformations in 4-Hydroxypyridinium Halides for Solar-Blind UV Functional
Jing Lu1,2, Xin Liu1,3, Shuangxiong Zhao1
1College of Chemistry, Beijing Normal University, Beijing, 100875, P.R. China.
Angewandte Chemie (International Ed. in English)
|January 5, 2026
Summary
Researchers developed twelve new 4-hydroxypyridinium halide crystals for advanced optical applications. These crystals exhibit large birefringence and nonlinear optical properties, offering broad transparency from solar-blind ultraviolet to near-infrared regions.
Area of Science:
- Materials Science
- Crystallography
- Optics
Background:
- Birefringent and nonlinear optical (NLO) crystals are essential for advanced optical technologies.
- Current challenges include achieving large birefringence (Δn), noncentrosymmetric (NCS) structures, and broad transparency (solar-blind UV to near-IR).
Purpose of the Study:
- To report a new family of twelve 4-hydroxypyridinium halide (4HPX) crystals.
- To investigate their structural transformations, optical properties, and potential for optical applications.
Main Methods:
- Synthesis and structural characterization of twelve 4HPX crystals.
- Analysis of optical properties, including bandgap, birefringence, and second-harmonic generation (SHG).
- Correlation of structural features (e.g., C─O bond lengths) with observed properties.
Main Results:
- The 4HPX family exhibits structural transformations from centrosymmetric to NCS phases dictated by solution acidity.
- These crystals possess large optical bandgaps exceeding known halogen polyanion-based crystals.
- Crystal II showed the largest Δn (0.293) in the family and among water-free SUV crystals; crystals I-V outperformed commercial materials.
- NLO crystals X-XII demonstrated SHG responses.
Conclusions:
- The 4HPX family offers a promising platform for developing next-generation birefringent and NLO materials.
- Rational design strategies based on cation-anion interactions and hydrogen bonding can tune optical properties.
- This study provides insights for creating crystals with desired optical characteristics for diverse applications.
Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.2K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
2.2K
01:01Acid Halides to Carboxylic Acids: Hydrolysis
3.5K
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic...
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic...
3.5K