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Schematic representation of the bulkiness effect on the magnitude of the supramolecular chirogenesis in the anti conformation of 1 upon interaction with monodentate guests.
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This feature article gives a general introduction to the phenomenon of supramolecular chirogenesis using the most representative examples of different chirogenic assemblies on the basis of ethane-bridged bis-porphyrinoids. Supramolecular chirogenesis is based upon a smart combination of supramolecular chemistry and chirality sciences and deals with...
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... bulkiness effect has been further investigated by varying the size of the guest. As the size of the bulkiest X substituent of the ligand is increased, whilst the size of the second bulky X' substituent remains unchanged, the dominant steric hindrance between the X substituent and the 3-ethyl group is enhanced ( Figure 6). In order to minimize this repulsive interaction, the screw angle between the two porphyrin moieties increases resulting in formation of the greater screw structure and subsequently yielding the more intense exciton couplet CD signal. ...
Citations
... Porphyrins play an important role in different fields of science and technology, including catalysis [1][2][3], light harvesting [4][5][6], medicine [7][8][9][10], supramolecular systems [11][12][13][14][15][16][17][18][19][20][21], electronic devices [16][17][18], etc. Besides, porphyrin-based systems have found broad application as chemical and chirality sensors [19][20][21][22] because of their notable property to form supramolecular assemblies with different guest molecules. These assemblies produce characteristic absorption bands in the low-energy regions of the corresponding UV-Vis and circular dichroism (CD) spectra, which are essentially shifted from absorption of the majority of analytes [23][24][25][26]. ...
... These assemblies produce characteristic absorption bands in the low-energy regions of the corresponding UV-Vis and circular dichroism (CD) spectra, which are essentially shifted from absorption of the majority of analytes [23][24][25][26]. Recently, much attention has also been paid to the phenomena of supramolecular chirogenesis, where a chiral guest determines the supramolecular chirality of the entire host-guest system upon binding to an achiral host molecule [12][13][14][15]20,[23][24][25][26][27][28][29][30][31][32][33][34][35]. In the case of ethane-bridged bis(zinc porphyrin)s (bis(ZnOEP)s) (Figure 1), steric hindrance induced by coordination of a chiral guest forces the supramolecular system to adopt a screw achiral host molecule [12][13][14][15]20,[23][24][25][26][27][28][29][30][31][32][33][34][35]. ...
... Recently, much attention has also been paid to the phenomena of supramolecular chirogenesis, where a chiral guest determines the supramolecular chirality of the entire host-guest system upon binding to an achiral host molecule [12][13][14][15]20,[23][24][25][26][27][28][29][30][31][32][33][34][35]. In the case of ethane-bridged bis(zinc porphyrin)s (bis(ZnOEP)s) (Figure 1), steric hindrance induced by coordination of a chiral guest forces the supramolecular system to adopt a screw achiral host molecule [12][13][14][15]20,[23][24][25][26][27][28][29][30][31][32][33][34][35]. In the case of ethane-bridged bis(zinc porphyrin)s (bis(ZnOEP)s) (Figure 1), steric hindrance induced by coordination of a chiral guest forces the supramolecular system to adopt a screw conformation, with the chirality of a guest determining either a clockwise or anticlockwise arrangement of porphyrin units in the bis-porphyrin host [30][31][32]. ...
The complexation of (3aR,7aR)-N-(3,5-bis(trifluoromethyl)phenyl)octahydro-2H-benzo[d]imidazol-2-imine (BTI), as a guest, to ethane-bridged bis(zinc octaethylporphyrin), bis(ZnOEP), as a host, has been studied by means of ultraviolet-visible (UV-Vis) and circular dichroism (CD) absorption spectroscopies, single crystal X-ray diffraction, and computational simulation. The formation of 1:2 host-guest complex was established by X-ray diffraction and UV-Vis titration studies. Two guest BTI molecules are located at the opposite sides of two porphyrin subunits of bis(ZnOEP) host, which is resting in the anti-conformation. The complexation of BTI molecules proceed via coordination of the imine nitrogens to the zinc ions of each porphyrin subunit of the host. Such supramolecular organization of the complex results in a screw arrangement of the two porphyrin subunits, inducing a strong CD signal in the Soret (B) band region. The corresponding DFT computational studies are in a good agreement with the experimental results and prove the presence of 1:2 host-guest complex as the major component in the solution (97.7%), but its optimized geometry differs from that observed in the solid-state. The UV-Vis and CD spectra simulated by using the solution-state geometry and the TD-DFT/ωB97X-D/cc-pVDZ + SMD (CH2Cl2) level of theory reproduced the experimentally obtained UV-Vis and CD spectra and confirmed the difference between the solid-state and solution structures. Moreover, it was shown that CD spectrum is very sensitive to the spatial arrangement of porphyrin subunits.
... Porphyrinoid based supramolecular structures so far have attracted much attention for chirality-sensing purposes, owing to their appropriate chemical, physico-chemical, and spectral properties, easy handling and versatile modification, direct relation to many biological processes, and wide applicability (Borovkov et al., , 2014. This prompted us to apply porphyrinoid-based supramolecular systems for design and development of smart chirality sensors (Borovkov et al., , 2010. Our supramolecular chirality sensing systems are based on a simple structural motif, syn conformation of ethane-linked bis-porphyrin, (syn-1, M,M' = Zn, Mg, 2H) ( Figure 1). ...
... The selective excitation of charge-transfer (CT) complex and the direct excitation of stilbene gave distinctly different product ratios and diastereomeric excesses (de's) clearly demonstrated that the excited CT complex (ECT) and the conventional exciplex (EX) differ in structure and reactivity. In order to test the generality of such observations, we have then examined the wavelength dependences on the Paternò-Büchi reaction of chiral p-cyanobenzoates with 1,1-diphenylethene (Matsumura et al., 2009 and2010) and on the diastereoselective photocyclization of intramolecular donor-acceptor systems (Nishiuch et al., 2012). In all the cases examined, the apparent de values observed were different in each excitation mode. ...
Herein we report the discovery of C3 symmetric opioid architectures as efficient DNA binding molecules. To our knowledge these agents are the first opioid-based structures with nucleic acid recognition properties. These architectures may now pave the way toward the development of a new class of semi-synthetic DNA binding
molecule with potential applications in gene delivery.
... Porphyrinoid based supramolecular structures so far have attracted much attention for chirality-sensing purposes, owing to their appropriate chemical, physico-chemical, and spectral properties, easy handling and versatile modification, direct relation to many biological processes, and wide applicability (Borovkov et al., , 2014. This prompted us to apply porphyrinoid-based supramolecular systems for design and development of smart chirality sensors (Borovkov et al., , 2010. Our supramolecular chirality sensing systems are based on a simple structural motif, syn conformation of ethane-linked bis-porphyrin, (syn-1, M,M' = Zn, Mg, 2H) ( Figure 1). ...
... The selective excitation of charge-transfer (CT) complex and the direct excitation of stilbene gave distinctly different product ratios and diastereomeric excesses (de's) clearly demonstrated that the excited CT complex (ECT) and the conventional exciplex (EX) differ in structure and reactivity. In order to test the generality of such observations, we have then examined the wavelength dependences on the Paternò-Büchi reaction of chiral p-cyanobenzoates with 1,1-diphenylethene (Matsumura et al., 2009 and2010) and on the diastereoselective photocyclization of intramolecular donor-acceptor systems (Nishiuch et al., 2012). In all the cases examined, the apparent de values observed were different in each excitation mode. ...
... Furthermore, these compounds have turned out to be particularly well suited for investigating different chiral processes and, particularly, supramolecular chirality, because of their specific and highly appropriate spectral, physico-chemical and synthetic characteristics, facile handling and superior propensity to form various supramolecular assemblies [2]. Furthermore, this kind of molecular and supramolecular system, so far, has attracted considerable attention of the scientific OPEN ACCESS community on account of the wide applicability in different fields of fundamental and applied sciences and modern technologies lying behind the judicious design of various chiroptical devices and sensors, molecular switches and machines, enantioselective materials and catalysts, as well documented in numerous reviews discussing these topics to a greater or lesser extent [3][4][5][6][7][8][9][10][11][12][13][14][15]. In general, chirality in the porphyrin-based supramolecular systems may be generated either via the intrinsic chiral modification of achiral porphyrinoids, by employing naturally occurring chiral pigments or via the external chiral field. ...
... The more rigidly ethane-linked bis-porphyrin, 105 ( Figure 28), was able to form the corresponding supramolecular chiral structures upon interaction, as with bidentate and with monodentate guests [5,15,[78][79][80][81][82][83][84][85][86]. In the case of enantiopure monoamines, the induced CD amplitude was in the range of 7.2-129.7 cm −1 ·M −1 . ...
Supramolecular chirality, being an intelligent combination of supramolecular chemistry and chiral science, plays a decisive role in the functioning of various natural assemblies and has attracted much attention from the scientific community, due to different applications in modern technologies, medicine, pharmacology, catalysis and biomimetic research. Porphyrin molecules are of particular interest to study this phenomenon owing to their unique spectral, physico-chemical and synthetic properties. This review highlights the most important types of chiral porphyrin structures by using the best-suited representative examples, which are frequently used in the area of supramolecular chirality.
In the present work, sixteen different zinc porphyrins (possessing different meso substituents) with and without a chiral guest were modelled using DFT and TD‐DFT approaches in order to understand the influence of various controlling factors on electronic circular dichroism (ECD) spectra. Two major aspects are influenced by these factors: excitation energy of the electronic transitions and their intensity. In the case of excitation energy, the influence increases in the following order: orientation of the peripheral substituents<substituent's nature<axial ligation. However, the deformation of the porphyrin plane does not affect the excitation energies. In the case of intensity, the influence increases as follows: substituent's nature<conrotatory orientation of the peripheral substituents<deformation of the porphyrin plane<disrotatory orientation of the peripheral substituents<axial ligation.
Circular dichroism (CD) is a convenient and widely used tool for investigating structures of chiral molecules. However, the unambiguous simulation of CD spectra is not a trivial task, because the accuracy of theoretical calculations depends on the nature of the system. In the present work, the induced CD spectra of six zinc porphyrin complexes with chiral guests were simulated by using different DFT methods. The best agreement between theoretical and experimental results for the Soret (B) band absorption region was achieved with the ωB97X-D, CAM-B3LYP, and M06-2X functionals by applying the SMD solvent model. Using DZVP basis sets allowed a good agreement between the simulated and experimental spectra, however accurate simulation of the length- and velocity rotational strengths needed larger TZVP basis sets. Additionally, it was shown how the conformation of the chiral guest influences the chirogenic mechanism.
This paper presents a succinct overview of recent advances of our research groups in the field of supramolecular chirogenesis and consequent progress towards functional chiral material. The phenomenon of supramolecular chirogenesis, which is a smart combination of supramolecular chemistry and chiral science, is demonstrated with one of the most representative structural motifs amongst chirogenic systems on the basis of ethane-bridged bis-porphyrinoids, whilst further progress towards functional chiral material is made upon chiral modification of metal surface that results in effective chiroptical applications including the asymmetric catalyst.
Four ZnII 5,10,15-triphenylporphyrin (TriPP) complexes meso–meso linked by two-atom bridges, namely, C2H2 (2), C2 (3), CH=N (4), and N2 (5), were prepared, for comparison of ground-state inter-porphyrin conjugation. The X-ray crystal structure of azoporphyrin 5·py2 (py = pyridine) was determined: it exhibits a stepped-offset shape and a porphyrin–azo torsion angle of 34.8°. Some new monoporphyrin starting materials were prepared, and ZnTriPPNH2 (27), ZnTriPPCHO (23), NiTriPPCHO (7), and ZnTriPPCH2CH2Ph (18), as well as the byproduct butadiyne-linked dimer 26 were characterized by single-crystal X-ray crystallography. The conjugation in the dimers was assessed by electronic absorption and steady-state fluorescence spectroscopy. All show variously split B bands: azoporphyrin 5 clearly has the strongest ground-state inter-porphyrin interactions. Imine 4 and azo 5 show strongly quenched fluorescence emission, which indicates the presence of efficient relaxation pathways afforded by the N-containing linkers.
This paper presents a succinct overview of recent advances of our research groups in the field of supramolecular chirogenic systems in the solution and in the solid state and consequent progress towards various functional materials having potential applications in different areas of science and technology. The phenomenon of supramolecular chirality, which is a smart combination of supramolecular chemistry and chiral science, is demonstrated with one of the most representative structural motifs amongst existing chirogenic systems, which is based upon the ethane-bridged bis-porphyrinoids. Further progress towards various functional materials is made upon preparation of different thin-films and nanostructures using the same bis-porphyrin architecture. For more practical application of functional materials chiral modification of metal surface is carried out resulting in effective asymmetric catalyst.
An indolocarbazole dimer that contains aldehyde groups at both ends was prepared by connecting two monomeric units through a rod-like 1,4-butadiynyl spacer. Upon mixing with chiral 1,2-diamines at room temperature, the dimer was in situ converted to the corresponding cyclic diimines in the presence of tetrabutylammonium acetate as a template. The resulting diimines fold to helical conformations of right-handed (P) or left-handed (M) orientations, depending on the absolute stereochemistries of chiral 1,2-diamines. The patterns and intensities of the CD spectra can be used to determine the absolute configurations and enantiomeric excesses of chiral 1,2-diamines.
