Vapochromic behaviour of a nickel(II)-quinonoid complex with dimensional changes between 1D and higher

Area of Science:

• Coordination Chemistry
• Materials Science
• Spectroscopy

Background:

• Vapochromism in metal-organic complexes is often linked to spin-state switching.
• Understanding the structural and electronic factors governing vapochromism is crucial for designing responsive materials.

Purpose of the Study:

• To investigate the vapochromic properties of the nickel(ii)-chloranilato complex, {Ni(ca)(VM)2}n.
• To elucidate the mechanism of vapochromism and compare it with other nickel-based complexes.

Main Methods:

• Synthesis and characterization of the nickel(ii)-chloranilato complex.
• Exposure to various vapors and subsequent drying to observe color changes.
• X-ray absorption fine structure (XAFS) analysis to study structural changes.
• Spin state analysis.

Main Results:

• The {Ni(ca)(VM)2}n complex displays reversible vapochromism upon exposure to and removal of vapors.
• Unlike related complexes, {Ni(ca)(VM)2}n does not exhibit spin-state switching.
• XAFS analysis confirms the maintenance of a six-coordinate geometry even after vapor removal.
• The observed vapochromism is attributed to dimensional changes and the weaker ligand field of the chloranilate ligand.

Conclusions:

• The nickel(ii)-chloranilato complex offers a novel example of vapochromism independent of spin-state switching.
• The structural integrity and weaker chloranilate ligand field are key factors in its unique vapochromic behavior.
• This finding expands the understanding of mechanisms driving responsive material behavior.