Chiral Bisporphyrin Supramolecular Systems And Sandwich Type Molecular Rotor Systems

1.Intramolecular chirality induction and intermolecular chirality modulation in BINOL bridged bisporphyrin hostsWe have studied the intra-and inter-molecular chirogenesis events on a family of chiral bisporphyrin hosts H1-H3.The three pairs of enantiomers for H1-H3 were constructed by connecting two zinc(II)porphyrinates to a homochiral(R)-(+)-or(S)-(-)-1,1'-bi-2-naphthol(BINOL)with ester or ether linkages.Split Cotton effects were observed for all of the bisporphyrin hosts.For each enantiomer,the sign of the bisignate CD couplets directly correlates to the stereostructure of the BINOL linker,namely a(R)-BINOL linker leads to a negative CD couplet and vise versa.The CD intensities of the hosts are decreasing from H1 to H3 along with the increasing of the length and flexibility of the chemical linkages between BINOL and porphyrin subunits.The predictable CD signs and regularly changed CD intensities demonstrate the defined intramolecular asymmetric information transfer,by which the chirality of a BINOL linker is translated to a preferred chiral twist in the inter-porphyrin arrangement with tunable efficiency.Furthermore,the intermolecular binding of 4,4'-BiPyridyl(BiPy)and(S)-/(R)-DACH,as typical achiral and chiral ditopic guests,to the series of hosts were detected by UV-Vis,1H NMR and CD spectroscopic titrations.The spectroscopic titrations revealed that:1)BiPy coordinated with host H1-H3 can form 1:1 sandwich-type compounds,and the intensity of CD signals decreases significantly,though the sign does not change.2)While(S)-/(R)-DACH coordinated with H1 forming 1:2 open compounds,the intensity of CD signals decreases significantly and the sign does not change.3)(S)-/(R)-DACH coordinated with H2 and H3 forming 1:1 sandwich-type compounds,the binding processes afforded sensitive CD spectral changes in response to the stereostructure of chiral diamines.The observation is rationalized by DFT molecular modeling,which further confirmed the host-guest coordination mode and the two porphyrin twist direction.2.Chiral discrimination of diamines by a binaphthalene bridged porphyrin dimerA pair of 1,1'-binaphthalene bridged bisporphyrins(R)-and(S)-H1 were designed to examine their chiral discrimination abilities towards a range of model diamines by using UV-Vis absorption,CD and 1H NMR spectroscopies with the assistance of DFT molecular modeling.The spectroscopic titrations revealed that(R)-/(S)-H1 could encapsulate(R)-/(S)-DACH and(R)-/(S)-PPDA in the chiral bisporphyrin cavities,leading to the selective formation of sandwich-type 1:1 complexes via dual Zn-N coordination interactions.In particular,the chiral recognition energy(?G°)towards(R)-/(S)-DACH was evaluated to be-4.02 kJ mol-1.The binding processes afforded sensitive CD spectral changes in response to the stereostructure of chiral diamines.Remarkable enantiodiscrimination effects were also detected in the NMR titrations of(R)-/(S)-H1,in which the nonequivalent chemical shift(???)can reach up to 0.57 ppm for(R)-/(S)-DACH.However,due to the large steric effect,another chiral diamine((R)-/(S)-DPEA)could not be sandwiched in the chiral bisporphyrin cavity,therefore(R)-/(S)-DPEA could hardly be discriminated by(R)-/(S)-H1.The present results demonstrate a chiral bisporphyrin host with integrated CD and NMR chiral sensing functions,and also highlight the binding mode-dependent character of its enantiodiscrimination performance for different chiral guests.3.Binaphthol-strapped chiral bis(porphyrinato)cerium double-decker complexes(R)-(+)-or(S)-(-)-1,1'-bi-2-naphthol(BINOL)was applied as a remote chiral auxiliary to connect the two facing porphyrin rings,resulting in the BINOL-strapped chiral bis(porphyrinato)cerium double-decker complexes(R)-/(S)-1 and(R)-/(S)-2,which were carefully characterized by a range of spectroscopic and electrochemical methods.Perfect mirror images were observed in their circular dichroism(CD)spectra with a negative sign in the Soret band for(R)-enantiomers and a positive sign for(S)-enantiomers,which suggests the C2-chirality of a BINOL strap is transcribed to the double-decker core as a defined chiral twist in the inter-porphyrin arrangement.Furthermore,the CD intensities of(R)-/(S)-1 are always larger than those of(R)-/(S)-2,indicating that the intramolecular chirality transfer efficiency can be finely tuned by changing the length of interlocking moieties.4.Chiral molecular rotors with binaphthol-strapped mixed(phthalocyaninato)(porphyrinato)rare earth triple-deckersBinaphthol-strapped mixed(phthalocyaninato)(porphyrinato)rare earth triple-decker complexes(R)-/(S)-1 and(R)-/(S)-2 were synthesized to construct novel molecular rotors with phthalocyanine as rotator and two outer porphyrins bridged by substituted binaphthol as stators.Their rotation behaviors were studied by variable temperature 1H NMR(VT 1H NMR)experiments and line shape analysis.From the line shape analysis,for(R)-1 the rotation barriers Ea were 57.8 kJ mol'1 and 60.2 kJ mol-1,and for(R)-2 the rotation barrier Ea were 50.0 kJ mol'1 and 40.5 kJ mol-1 in[D8]toluene and CDC13 respectively.It indicated that the rotation barriers for(R)-1 were larger than those for(R)-2.These results suggest that the rotation rate of the rotator phthalocyanine can be tuned by the radius of coordination metal ions.5.Photocontrolled molecular rotor based on azobenzene-strapped mixed(phthalocyaninato)(porphyrinato)rare earth triple-deckersA new type of photocontrolled molecular rotor has been synthesized successfully,which is constructed by azobenzene group and(phthalocyaninato)(porphyrinato)rare earth triple-decker.It was characterized by MALDI-TOF mass spectrometry,nuclear magnetic resonance spectroscopy and electron absorption spectroscopy.The cis-trans isomerization was studied by UV and NMR spectroscopy and the ratio of cis/trans isomer was 76:24 after irradiation with 365 nm wavelength light for 20 minutes.The rotation rate of the phthalocyanine ligand in the cis-structure was higher than that in the trans-structure,indicating that the rotation of compound 1 could be successfully controlled by light.