Photoluminescent and ferroelectric properties of a chiral rhenium(I) complex based on the chiral (−)-4,5-pinene-2,2′-bipyridine ligand

Dinuclear Rhenium Complexes with a Bridging Helicene-bis-bipyridine Ligand: Synthesis, Structure, and Photophysical and Chiroptical Properties

By attaching pyridine groups to a diaza[6]helicene, a helical, bis-ditopic, bis-N N-coordinating ligand can be accessed. Dinuclear rhenium complexes featuring this bridging ligand, of the form [{Re(CO)3 Cl}2 (N N-N N)], have been prepared and resolved to give enantiopure complexes. These complexes are phosphorescent in solution at room temperature under one- and two-photon excitation. Their experimental chiroptical properties (optical rotation, electronic circular dichroism and circularly polarized emission) have been measured. They show, for instance, emission dissymmetry factors of c.a. ±3x10-3 . Quantum-chemical calculations indicate the importance of stereochemistry on the optical activity, pointing towards further design improvements in such types of complexes.

A pair of 2D chiral Ag(i) enantiomers with dual chiral elements: syntheses, structures, and photoluminescent and chiroptical properties

In this work, two new enantiopure bis-monodentate N-donor chiral ligands, namely (-)/(+)-2-(4'-pyridyl)-4,5-pinene-pyridine (L R /L S ), have been designed and synthesized. Using L R and L S as bridging ligands to react with AgClO4, a pair of novel 2D chiral Ag(i) enantiomers formulated as [Ag2(L R )2(ClO4)2] n (R-1) and [Ag2(L S )2(ClO4)2] n (S-1) were isolated and characterized. In R-1 and S-1, each Ag(i) ion is bonded by two N atoms from two different chiral L R or L S ligands, leading to the formation of 1D right- or left-handed -L-Ag(i)-L- helical chains. Moreover, two adjacent helical chains are further doubly linked by two monodentate ClO4 - anions through weak Ag-O contacts to form 2D network structures, in which dual chiral elements, i.e., center chirality and helical chirality coexist. Interestingly, each free ligand L R /L S and R-1/S-1 enantiomers show very different ECD spectra in the solid state and in solution, which are correlated to the intermolecular interactions and molecular structures in each state, respectively. Notably, as a representative, R-1 exhibits intense room temperature photoluminescence both in the solid state and in solution with different emission features and mechanisms, while it also shows more intense emission than that of free ligand L R . In particular, R-1 and S-1 represent the first examples of 2D Ag(i) chiral coordination polymers (CCPs) supported by ClO4 - anions, possessing dual chiral elements.

Synthesis and structure of a cobalt coordination polymer based on 2,8-di(pyridin-4-yl)dibenzothiophene and 4,4-dicarboxydiphenylsulfone

A new coordination polymer {[Co2(DPDBT)2(DCPS)2(H2O)](H2O)} n (1) [DPDBT = 2,8-di(pyridin-4-yl)dibenzothiophene, H2DCPS = 4,4′-dicarboxydiphenyl sulfone], was synthesized under solvothermal conditions. Complex 1 exhibits a 2D structure with two different kinds of binuclear cobalt cluster units. The UV/Vis spectra of 1 and of the ligands were investigated, indicating that complex 1 is a potential wide gap semiconductor material.

enantio-Enriched CPL-active helicene-bipyridine-rhenium complexes

The incorporation of a rhenium atom within an extended helical π-conjugated bi-pyridine system impacts the chiroptical and photophysical properties of the resulting neutral or cationic complexes, leading to the first examples of rhenium-based phosphors that exhibit circularly polarized luminescence.

Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes

Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene-bipyridine proligand 1 a and in its "rollover" cycloplatinated derivative 2 a. Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum-chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene-bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge-transfer-type transition rather than a π-π* transition) as well as an increase in the HOMO-LUMO character of the transition and stabilization of the LUMO level upon protonation.

A pair of dinuclear Re(i) enantiomers: synthesis, crystal structures, chiroptical and ferroelectric properties

A pair of dinuclear Re(i) enantiomers have been successfully synthesized, representing the first example of polynuclear Re(i) complexes with ferroelectric properties and possessing a multifunctional feature combining chirality, NLO-activity and ferroelectricity within one molecule.