Vibronic Coupling Explains the Different Shape of Electronic Circular Dichroism and of Circularly Polarized Luminescence Spectra of Hexahelicenes

Liu, Yanli; Cerezo, Javier; Mazzeo, Giuseppe; Lin, Na; Zhao, Xian; Longhi, Giovanna; Abbate, Sergio; Santoro, Fabrizio

doi:10.1021/acs.jctc.6b00109

Cited by 62 publications

(58 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the present situation, it is also likely that the dependence of the magnetic and electric transition dipoles on the torsional motion cannot be disregarded. The full consideration of such an effect cannot be accomplished at a pure electronic level and it would require the inclusion of vibronic contributions beyond the Franck–Condon approximation …”

Section: Resultsmentioning

confidence: 99%

Circularly Polarized Luminescence from Axially Chiral BODIPY DYEmers: An Experimental and Computational Study

Zinna

Bruhn

Guido

et al. 2016

Chemistry A European J

131

View full text Add to dashboard Cite

With our new home-built circularly polarized luminescence (CPL) instrument, we measured fluorescence and CPL spectra of the enantiomeric pairs of two quasi-isomeric BODIPY DYEmers 1 and 2, endowed with axial chirality. The electronic circular dichroism (ECD) and CPL spectra of these atropisomeric dimers are dominated by the exciton coupling between the main π-π* transitions (550-560 nm) of the two BODIPY rings. Compound 1 has strong ECD and CPL spectra (g =4×10 ) well reproduced by TD-DFT and SCS-CC2 (spin-component scaled second-order approximate coupled-cluster) calculations using DFT-optimized ground- and excited-state structures. Compound 2 has weaker ECD and CPL spectra (g =4×10 ), partly due to the mutual cancellation of electric-electric and electric-magnetic exciton couplings, and partly to its conformational freedom. This compound is computationally very challenging. Starting from the optimized excited-state geometries, we predicted the wrong sign for the CPL band of 2 using TD-DFT with the most recommended hybrid and range-separated functionals, whereas SCS-CC2 or a DFT functional with full exact exchange provided the correct sign.

show abstract

Section: Resultsmentioning

confidence: 99%

Circularly Polarized Luminescence from Axially Chiral BODIPY DYEmers: An Experimental and Computational Study

Zinna

Bruhn

Guido

et al. 2016

Chemistry A European J

131

View full text Add to dashboard Cite

show abstract

“…CPL simulations based on vertical transition energies and transition moments were also performed, but with inconsistent results (see SI). It is likely that the vibronic emission spectra need to be simulated [17] in order to replicate the experimental dissymmetry factors, which is beyond the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Chiroptical Properties of Hexa‐, Octa‐, and Deca‐azaborahelicenes: Influence of Helicene Size and of the Number of Boron Atoms

Shen

Srebro‐Hooper

Jean

et al. 2016

Chemistry A European J

115

View full text Add to dashboard Cite

Four members of a new class of cycloborylated hexa- to deca-helicenes (1a–d) have been prepared in enantiopure forms, along with cycloplatinated deca-helicenes (1d′, 1d1) further extending a family of cycloplatinated hexa- to octa-helicenes reported previously. The azabora[n]helicenes display intense electronic circular dichroism and strong optical rotations, whose dependence on the size of the helix (n = 6, 8, or 10) and number of boron atoms (1 or 2) has been examined in detail both experimentally and theoretically. The photophysical properties (unpolarized and circularly polarized luminescence) of these new fluorescent organic helicenes have been measured and compared with the corresponding organometallic phosphorescent cycloplatinated derivatives (1a1–d1).

show abstract

“…The electronic transition that gives origin to the CPL activity should be similar to the one responsible of the absorption, so it should be correlated with the negative CD band. Possible vibronic effects may contribute to the intensity and the shape of CD and CPL bands . Indeed, despite the high noise level, one can see that CPL band shape and bandwidth for the L‐Phe case is slightly different from the other two cases.…”

Section: Resultsmentioning

confidence: 95%

A stereodynamic fluorescent probe for amino acids. Circular dichroism and circularly polarized luminescence analysis

et al. 2017

Self Cite

View full text Add to dashboard Cite

The use of stereodynamic probes is becoming one of the leading strategies for the fast and effective determination of enantiomeric excess. Recently, we reported a series of novel molecular architectures based on a modified tris(2-pyridylmethyl)amine complex (TPMA), which are able to amplify the electronic CD, in the case of Zn(II) assemblies and vibrational CD, in the case of Co(II) assemblies. Herein, we report a structural modification of the ligand with the purpose to obtain a fluorescent chiral probe. The study deals with the synthesis of the novel ligand, the formation of the self-assembly system with amino acids, and the study of the electronic CD and circularly polarized luminescence. KEYWORDS CD, CPL, enantiomeric excess, self-assembly, supramolecular chemistry | INTRODUCTIONIn the last few decades, several research groups have been studying chiral sensors because of the important applications that chiral molecules have in several fields of science, ranging from catalysis to materials. Under this respect, special attention has been paid to searching new methods and techniques for the determination of enantiomeric excess (ee) that are faster and cheaper than traditional chromatographic methods. [1][2][3][4] In this context, several supramolecular architectures have been developed to gather an optical signal that can be easily measured through the most common spectroscopic techniques, ie, circular dichroism (CD). [5][6][7][8][9][10][11][12][13][14][15] Usually, these supramolecular sensors possess at least one labile stereogenic element that interconverts between 2 enantiomeric forms. The addition of a chiral analyte leads preferentially to the formation of one diasteroisomer that furnishes back the optical chiral information. Within these stereodynamic probes, tris(2-pyridylmethyl)amine (TPMA)-based metal complexes have shown to be versatile chemical systems for the determination of ee. [16][17][18][19][20][21][22] This ligand assumes a propeller-like arrangement around the metal center that in solution is in equilibrium between the two helical configurations (clockwise and counterclockwise configuration is preferred, and the resulting diasteroisomer is able to provide a chiroptical signal. 23,24 Recently, we have started to combine the TPMA scaffold with dynamic covalent chemistry (DCC) of imines formation. [25][26][27][28][29]31 has already shown its fundamental role in the formation of new complex nano-architectures. In particular, we described two novel supramolecular architectures based on modified TPMA metal complexes (Scheme 1): the dinuclear 1-Zn-aa and 3-Zn-aa, and the trinuclears 2-Zn-aa and 2-Co-aa. These systems have shown to perform as probes for amino acids, 32-35 furnishing dichroic signals characteristic of the amino acidic side chain and proportional to the enantiomeric excess. While all systems are effective using electronic CD, the presence of cobalt(II) in 2-Co-aa induces additionally gigantic (or: huge) vibrational CD bands, allowing the measurement of a VCD spectrum in onl...

show abstract

Vibronic Coupling Explains the Different Shape of Electronic Circular Dichroism and of Circularly Polarized Luminescence Spectra of Hexahelicenes

Cited by 62 publications

References 61 publications

Circularly Polarized Luminescence from Axially Chiral BODIPY DYEmers: An Experimental and Computational Study

Circularly Polarized Luminescence from Axially Chiral BODIPY DYEmers: An Experimental and Computational Study

Synthesis and Chiroptical Properties of Hexa‐, Octa‐, and Deca‐azaborahelicenes: Influence of Helicene Size and of the Number of Boron Atoms

A stereodynamic fluorescent probe for amino acids. Circular dichroism and circularly polarized luminescence analysis

Contact Info

Product

Resources

About