Molecular-Engineered Biradicals Based on the Y^III-Phthalocyanine Platform

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Phthalocyanine and porphyrin macrocycles are key components in advanced materials.
• Yttrium(III) double-decker complexes offer unique magnetic and electronic properties.
• Tethering such complexes allows for the creation of novel molecular architectures with tunable functionalities.

Purpose of the Study:

• To synthesize and characterize novel mixed-ligand phthalocyanine/porphyrin yttrium(III) double-decker complexes.
• To create biradicals by coupling these double-decker complexes through rigid organic tethers.
• To investigate the magnetic properties and spin delocalization in these biradicals using advanced spectroscopic techniques.

Main Methods:

• Synthesis of a custom-made porphyrin ligand and subsequent formation of a mixed-ligand yttrium(III) double-decker complex (DD).
• Glaser and Sonogashira coupling reactions to synthesize short-tethered (C1) and long-tethered (C2, C3) biradicals.
• Pulsed electron paramagnetic resonance techniques including Field-Swept Echo-Detected (FSED), saturation recovery, and spin nutation experiments.
• Density Functional Theory (DFT) calculations to determine conformational stability and spin distribution.

Main Results:

• The synthesized double-decker complex (DD) exhibited magnetic properties similar to the parent [Y(pc)2]• complex.
• Biradicals C2 and C3 showed spectral broadening in FSED experiments due to dipolar interactions, with satellite features indicating spin delocalization on the tether.
• DFT calculations confirmed the stability of the trans conformation and significant spin delocalization ('spin leakage') over the organic tether, particularly in C1.

Conclusions:

• The successful synthesis of yttrium(III) phthalocyanine/porphyrin double-decker biradicals was achieved.
• Evidence of spin delocalization through rigid tethers was observed, suggesting potential for tuning electronic communication in molecular systems.
• The shortest biradical, C1, displayed the most pronounced spin leakage, highlighting the influence of tether length on electronic coupling.