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Red to Green Switch Driven by Order in an Ionic Ir III Liquid‐Crystalline Complex
Author(s) -
Szerb Elisabeta I.,
Talarico Anna M.,
Aiello Iolinda,
Crispini Alessandra,
Godbert Nicolas,
Pucci Daniela,
Pugliese Teresa,
Ghedini Mauro
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201000462
Subject(s) - phosphorescence , chemistry , mesophase , luminescence , amorphous solid , cationic polymerization , crystallography , phase (matter) , electroluminescence , triphenylene , photochemistry , fluorescence , molecule , polymer chemistry , materials science , organic chemistry , optics , physics , optoelectronics , layer (electronics)
New cationic Ir III materials of general formula [Ir(ppy) 2 (C n ‐bpy)]PF 6 {H(ppy) = 2‐phenylpyridine; C n ‐bpy = 3,4,5‐R‐4,4′‐benzoyloxymethyl‐2,2′‐bipyridine; n = 8, R = OC 8 H 17 ; n = 0, R = H} were synthesised and fully characterised. Both complexes show high phosphorescence quantum yields in their condensed phases. Moreover, the introduction of long alkoxy chains on the bipyridne ligand in [Ir(ppy) 2 (C 8 ‐bpy)]PF 6 ( 1 ) has induced mesomorphism, and consequently a dynamic functional material with properties modulated by external stimuli has been obtained. Starting from the isotropic phase, on slow cooling a crystalline phase characterised by a bright green emission is obtained. However, on fast cooling a kinetically favoured columnar hexagonal mesophase is preferentially formed, which is stable down to room temperature. In this phase, the high luminescence is still maintained, even if a switch to yellow emission colour is observed. Moreover, through spin coating of solutions of 1 , it has been possible to obtain its amorphous thin film to accomplish a further shift of the emission wavelength in the orange‐red spectral range. A fully reversible colour tuning process by surface stress and heating from the orange‐red film to the green crystalline phase, indicative of a mechanochromic behaviour, is also achieved.