HX-Linear and Nonlinear Optical Responsiveness of Rationally Designed Heteroleptic d⁸-Metallo-dithiolene Complexes.

Area of Science:

• Coordination Chemistry
• Materials Science
• Chemical Sensing

Background:

• Heteroleptic dithiolene complexes featuring metal centers (Ni, Pd, Pt) and chiral acceptor ligands offer unique electronic and optical properties.
• The development of responsive materials for sensing and nonlinear optics is a key area in materials science.

Purpose of the Study:

• To investigate the acid- and ammonia-responsiveness of novel heteroleptic donor-M-acceptor dithiolene complexes.
• To evaluate the potential of these complexes as optical sensors and for nonlinear optical applications.

Main Methods:

• Synthesis and characterization of Ni(II), Pd(II), and Pt(II) dithiolene complexes.
• Spectroscopic analysis (UV-Vis) to study color changes upon acid and ammonia exposure.
• Fabrication of cellulose-supported films and polymer-embedded matrices for sensing and nonlinear optical measurements.
• Density Functional Theory (DFT) and time-dependent DFT calculations to elucidate structure-property relationships.

Main Results:

• Complexes 1, 2, and 3 showed a significant bathochromic shift and color change upon addition of hydrohalic acids, reversible with ammonia.
• Cellulose films of complex 1 demonstrated effective optical sensing of HCl vapors and triethylamine.
• Reversible switching of nonlinear optical properties (chemical second harmonic generation) was achieved in polymer matrices upon sequential exposure to HCl and NH3.

Conclusions:

• The studied dithiolene complexes exhibit excellent HX-responsiveness, enabling their use as optical sensors.
• The reversible switching of nonlinear optical properties demonstrates their potential in photonic devices.
• DFT calculations provide insights into the structure-property correlations, guiding future material design.