Inherently Chiral Macrocyclic Oligothiophenes: Easily Accessible Electrosensitive Cavities with Outstanding Enantioselection Performances

Abstract

Linear conjugated oligothiophenes of variable length and different substitution pattern are ubiquitous in technologically advanced optoelectronic devices, though limitations in application derive from insolubility, scarce processability and chain-end effects. This study describes an easy access to chiral cyclic oligothiophenes constituted by 12 and 18 fully conjugated thiophene units. Chemical oxidation of an “inherently chiral” sexithiophene monomer, synthesized in two steps from commercially available materials, induces the formation of an elliptical dimer and a triangular trimer endowed with electrosensitive cavities of different tunable sizes. Combination of chirality with electroactivity makes these molecules unique in the current oligothiophenes literature. These macrocycles, which are stable and soluble in most organic solvents, show outstanding chiroptical properties, high circularly polarized luminescence effects and an exceptional enantiorecognition ability.

Multifunctional π-expanded oligothiophene macrocycles

“…The high symmetry of the cyclic structures of C10T-C35T influences their photophysical properties: the absorption maxima corresponding to an S 0 -S 2 electronic transition were red-shifted and showed a hyperchromic effect with an increase in the ring size. 27 These macrocycles showed chiroptical properties, circularly polarized luminescence effects, View Article Online and enantiorecognition ability. 1.0 nm, and adjacent thiophene units were twisted up and down by 26-341 to release the ring strain.…”

Searching for Models Exhibiting High Circularly Polarized Luminescence: Electroactive Inherently Chiral Oligothiophenes

“…The materials, derived from the oxidation of the enantiomerso ft he 2,2'-bis(2,2'-bithiophene-5-yl)-3,3'-bithianaphthene (1)( BT 2 -T 4 ), are the first examples of this new class of chiralp olyheterocycles. [2] The films resulting from both chemical and electrochemical oxidation of the opticala ntipodes of BT 2 -T 4 ,m ainly constituted by D 2 and D 3 cyclic dimers and trimers, [3] showed impressive chiroptical activity and outstanding enantiorecognition properties, in particular as electrodes urfaces. [2] The films resulting from both chemical and electrochemical oxidation of the opticala ntipodes of BT 2 -T 4 ,m ainly constituted by D 2 and D 3 cyclic dimers and trimers, [3] showed impressive chiroptical activity and outstanding enantiorecognition properties, in particular as electrodes urfaces.…”

“…In these systems, the atropisomeric scaffold, that is, the 3,3'-bithianaphthene, is decorated with two bithiopheneu nits ( Figure 1). [4] Furthermore, they exhibitedr emarkable circularly polarized luminescence( CPL) spectra, [3] with large g ratios reaching10 À2 ,d ifferentlyt ow hat observed for "classical" chiralp olythiophenesc haracterizedb y chiralp endants, that exhibit limited CPL activity. [4] Furthermore, they exhibitedr emarkable circularly polarized luminescence( CPL) spectra, [3] with large g ratios reaching10 À2 ,d ifferentlyt ow hat observed for "classical" chiralp olythiophenesc haracterizedb y chiralp endants, that exhibit limited CPL activity.…”

Self‐Standing Membranes Consisting of Inherently Chiral Electroactive Oligomers: Electrosynthesis, Characterization and Preliminary Tests in Potentiometric Setups

“…FT/IR‐4100 on ( i ) the BT 2 T 4 monomer ( ii ); a sample of electrodeposited oligo‐BT 2 T 4 film; ( iii ) a sample of closed BT 2 T 4 dimers; ( iv ) a sample of closed BT 2 T 4 trimers; ( v ) a sample of closed BT 2 T 4 tetramers. Samples ( iii ), ( iv ) and ( v ), representative of several film components (as confirmed by HR LDI) were studied for comparison, being available as previously obtained along an organic route . The film sample was electrodeposited from the BT 2 T 4 in deuterated acetonitrile (Aldrich)+0.1 M LiClO 4 (Aldrich) (a medium affording to minimize aliphatic C−H signals) followed by stability cycles in the monomer‐free solution (to eliminate monomer traces).…”

“…gratefully acknowledges financial support from Fondo per il Finanziamento delle Attività Base di Ricerca‐FFABR. The authors acknowledge Dr. Elsa Quartapelle Procopio for organic synthesis and separation of cyclic oligomers used as references, Dr. Alessio Orbelli Biroli for profilometry measurements, Claudia Malacrida for voltammetry enantiodiscrimination tests here mentioned (manuscript in preparation), Prof. Francesco Sannicolò and Prof. Sergio Abbate for fruitful discussions; the latter especially concerning the chiroptical study. The authors also acknowledge TGA‐DSC Mettler facilities available at SmartMatLab at Department of Chemistry, Università degli Studi di Milano, operated by Dr. Serena Cappelli; SEM facilities at Unitech (Università degli Studi di Milano), operated by Dr. Nadia Santo; and MALDI facilities at UNITECH COSPECT, operated by Dr. Marco Pappini.…”