The quest of new organic materials, for specific optoelectronic applications (including OLEDs, OFETs, photodetectors and OPVs), displaying high carrier mobility, strong optical absorptions and efficient luminescence, is urging. Organic polyconjugated systems (both small molecules and polymers) as well as polycyclic fused aromatic hydrocarbons represent a suitable fundamental class of molecules whose electronic properties and solid state intermolecular interactions can be varied, over a wide range, upon proper functionalization. Helicity coupled luminescent features is recently raising great interest in the scientific community for circularly polarized emission studies. In this perspective, tetrathia[7]helicenes, [7]THs, are chiral polycyclic aromatic compounds with nonplanar screw-shaped skeletons[1]. Formed by ortho-fused benzene and thiophene rings they display interesting luminescent features although scantly investigated[2]. To this aim, we have prepared and studied three new fluorinated [7]TH suited to investigate structure-property relationships in this molecular class. In this communication we report on the synthesis of fluorinated rac-[7]THs; their photophysical and electrochemical properties are compared to those of a parent [7]TH. [7]THs display deep blue fluorescence emissions with QY of 10% and subnanosecond lifetime. Low temperature PL studies reveal a green phosphorescence emission, being located at ca. 540 nm, barely observed before; its shape strongly depend from the functional groups R1and R2.. The fast radiative phosphorescence decay in the order of 100 ms, its bright intensity, as well as the small S1-T1 gap (ca. 6000-7000cm-1) are suggestive of a quite efficient spin orbit coupling mechanism affecting the excited state dynamics of these non planar conjugated molecules. In consideration of high energy triplet emission, given the size of the conjugated ?-system (featuring 7 ortho-condensed rings), theoretical TD-DFT calculations will be presented as well (scheme 1).
Tetrathia[7]helicenes, polyconjugated high triplet energy systems: synthesis, photophysics and electrochemical characterizations
A Bossi;
2018
Abstract
The quest of new organic materials, for specific optoelectronic applications (including OLEDs, OFETs, photodetectors and OPVs), displaying high carrier mobility, strong optical absorptions and efficient luminescence, is urging. Organic polyconjugated systems (both small molecules and polymers) as well as polycyclic fused aromatic hydrocarbons represent a suitable fundamental class of molecules whose electronic properties and solid state intermolecular interactions can be varied, over a wide range, upon proper functionalization. Helicity coupled luminescent features is recently raising great interest in the scientific community for circularly polarized emission studies. In this perspective, tetrathia[7]helicenes, [7]THs, are chiral polycyclic aromatic compounds with nonplanar screw-shaped skeletons[1]. Formed by ortho-fused benzene and thiophene rings they display interesting luminescent features although scantly investigated[2]. To this aim, we have prepared and studied three new fluorinated [7]TH suited to investigate structure-property relationships in this molecular class. In this communication we report on the synthesis of fluorinated rac-[7]THs; their photophysical and electrochemical properties are compared to those of a parent [7]TH. [7]THs display deep blue fluorescence emissions with QY of 10% and subnanosecond lifetime. Low temperature PL studies reveal a green phosphorescence emission, being located at ca. 540 nm, barely observed before; its shape strongly depend from the functional groups R1and R2.. The fast radiative phosphorescence decay in the order of 100 ms, its bright intensity, as well as the small S1-T1 gap (ca. 6000-7000cm-1) are suggestive of a quite efficient spin orbit coupling mechanism affecting the excited state dynamics of these non planar conjugated molecules. In consideration of high energy triplet emission, given the size of the conjugated ?-system (featuring 7 ortho-condensed rings), theoretical TD-DFT calculations will be presented as well (scheme 1).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
