Red to Green Switch Driven by Order in an Ionic IrIII Liquid-Crystalline Complex

Authors

  • Elisabeta I. Szerb,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Anna M. Talarico,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Iolinda Aiello,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Alessandra Crispini,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM, Dipartimento di Scienze Farmaceutiche, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy
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  • Nicolas Godbert,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Daniela Pucci,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Teresa Pugliese,

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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  • Mauro Ghedini

    1. Centro di Eccellenza CEMIF.CAL, LASCAMM – CR INSTM, Unità INSTM della Calabria and LiCryl, CNR-INFM Dipartimento di Chimica, Università della Calabria, 87036 Arcavacata di Rende (CS), Italy, Fax: +39-0984-492066
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Abstract

New cationic IrIII materials of general formula [Ir(ppy)2(Cn-bpy)]PF6 {H(ppy) = 2-phenylpyridine; Cn-bpy = 3,4,5-R-4,4′-benzoyloxymethyl-2,2′-bipyridine; n = 8, R = OC8H17; 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(C8-bpy)]PF6 (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.

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