A Spin‐Active, Electrochromic, Solvent‐Free Molecular Liquid Based on Double‐Decker Lutetium Phthalocyanine Bearing Long Branched Alkyl Chains

Synthesis and characterization of a novel, multifunctional, solvent‐free room‐temperature liquid based on alkylated double‐decker lutetium(III) phthalocyanine (Pc2Lu) are described. Lowering of the melting point and viscosity of intrinsically solid Pc2Lu compounds has been achieved through the attachment of flexible, bulky, and long branched‐alkyl chains, that is, thio‐2‐octyldodecyl, to the periphery of the Pc2Lu unit. The embedded Pc2Lu unit maintains its inherent molecular functions, such as spin‐active nature and electrochromic behavior in the liquid state. Comparison of the properties with a solid‐like Pc2Lu derivative, functionalized with shorter alkyl chains, that is, thio‐2‐ethylhexyl, underlines the importance of the hampering effect on the π–π interactions of neighboring Pc2Lu molecules by bulkier and longer branched‐alkyl chains. This study could possibly pave the way for novel multifunctional liquids whose spin‐activities are associated with their rheological or optoelectronic properties. It's fluid now! An amorphous and liquid lutetium phthalocyanine (Pc2Lu) was developed. The π‐cores of Pc2Lu are embedded in flexible, bulky, and branched long alkyl chains, and thus shielded well from the environment. The inherent molecular functions of Pc2Lu, such as spin‐active nature and electrochromic behavior are maintained even in the neat liquid state at room temperature.