Search

A series of bola-type dipeptides based on an Ala–Phe building block was synthesized by altering the chirality of Ala and Phe. They were able to self-assemble into right- or left-handed helical nanofibers in a mixture of methanol and water. Both the handedness of the nanofibers and that of the molecular stacking were controlled by the chirality of the phenylalanine residue. 1H NMR, circular dichroism and FT-IR characterizations indicated that the formation of the nanofibers was driven by the hydrophobic association of the hydrocarbon chains, π–π stackings of the phenyl rings and hydrogen bonds. X-ray diffraction patterns showed that the diastereoisomers packed into different structures. These bola-type Ala–Phe dipeptides can be potentially used for 3D printing.

We have investigated the structures of zinc and copper complexes of malonamide-linked bisporphyrin. Two porphyrin moieties adopt anti-configurations in both complexes. The linker (malonamide) plays important roles: it is involving in both coordination bonds and hydrogen bonds with coordinated water in zinc complex; it is involving in both inter- and intra-molecular hydrogen bonds in copper complex. Those supramolecular interactions lead to dimeric structures in both complexes. The dimerization constant of the zinc species has been evaluated by NMR method.

Chirality transfer has been investigated with an m-phthalic diamide-linked zinc bisporphyrinate as host and chiral monoalcohols with different alkyl substituents as guests. The substituent of the guest alcohol had a significant effect on chirality transfer. An increase in the number of carbon atoms from one to three resulted in circular dichroism (CD) sign inversion for the corresponding host-guest complexes. The crystal structures of these zinc bisporphyrinate-monoalcohol complexes revealed two types of orientation for the phenyl ring of the guests: one with the phenyl ring facing the porphyrin plane, and the other with the phenyl ring towards the linker. The chirality transfer mechanism was further studied by DFT and revealed that adjusting the chain length of the alkyl substituent could control the steric interaction between the alkyl group and the porphyrin plane, resulting in different chirality transfer outcomes. © 2018 Elsevier Ltd

2,3,7,8,12,13,17,18-Octabromo-5-(2-nitrophenyl)-10,15,20-triphenyl porphyrin (H[Formula: see text]OBP-NO[Formula: see text] and its metallic complexes have been designed and synthesized. Both the free-base porphyrin and its iron(III) complex have been characterized by X-ray crystallography. Structures confirm there are three phenyl groups and one 2-nitrophenyl at meso positions and eight bromine atoms at [Formula: see text]-pyrrole positions. The crowded substituents cause the porphyrin plane to be distorted and become saddle shaped. The complexes were also characterized by NMR and UV-vis spectra. The UV-vis spectrum of the free-base porphyrin shows that substitution by eight bromine atoms at [Formula: see text]-pyrrole positions leads to a red shift of the bands.

The molecular structures of three porphyrinate derivatives have been determined by X-ray studies. Two derivatives, [Fe(TTP)(1-MeIm)[Formula: see text]] · 2C[Formula: see text]H[Formula: see text] and [Fe(T-[Formula: see text]-OCH[Formula: see text]PP)(BzHIm)[Formula: see text]] are iron(II) derivatives, whereas the third, [Fe(TMP)(BzHIm)[Formula: see text]]ClO[Formula: see text] · 2CHCl[Formula: see text], is an iron(III) species. The structure determinations provide evidence of the importance of steric effects, either from the axial ligand or the porphyrin ligand, in defining the overall stereochemistry.

Two β,β′-linked porphyrin-chlorin heterodimers have been successfully synthesized with 4-fluorophenyl or 4-chlorophenyl substituted aldehyde as starting reagents. But those aldehydes with bulkier substituents did not lead to the corresponding heterodimers. These porphyrin-chlorin heterodimers and their metallic complexes have been characterized by X-ray crystallography. In all the structures, the pyrroline group in chlorin moiety and the pyrrole group in porphyrin moiety are directly connected by a single bond. Pyrroline ring has two sp[Formula: see text] hybridized carbons. The direct bonding makes the porphyrin and chlorin moieties closely contact with each other, pyrroline group and the pyrrole group forms a dihedral angle of ~70°. If porphyrin-chlorin heterodimers have bulkier substituents, the close contact could cause too much repulsion. That is probably why they can not be synthesized. For nickel complexes, the chlorin planes show large saddling and moderate ruffling conformation. The C–H⋯[Formula: see text] interaction could contribute to the saddling conformation. The distorted core makes dihedral angles and metal to metal distances between porphyrin and chlorin plane much smaller than those in their copper complexes. Their NMR, UV-visible and fluorescence spectral data have also been briefly discussed.

A new porphyrin with a (phenylcarbamoyl)benzoic acid group (compound A) and its iron(III) complex [Fe(A)] were successfully synthesized. The crystal structure of [Fe(A)] was characterized by X-ray crystallography, which shows a dimeric structure through iron-carboxlate coordination bonds. By using methylene blue (MB) dye as a model pollutant, we studied the photocatalytic activity of [Fe(A)] under visible light. The system of [Fe(A)]/H2O2 exhibited high efficiency for the photodegradation of MB in water. Moreover, the recycling experiments confirmed the stability and reutilization of the catalyst.

We have investigated the chirality transfer from 1-phenylethylamine to a 5-amino-1,3-phthalic acid diamide-linked zinc bisporphyrinate through crystallographic and DFT studies. When the hosts were mixed with optically pure 1-phenylethylamine, CD showed moderate signals in the Soret band region. Single crystals of the corresponding 1:1 and 1:2 host-guest complexes were obtained. We present the first crystallographic structure of a 1:2 host-guest complex consisting of a bisporphyrin host and chiral monoamine guests. The structure reveals that the host-guest interactions are different for two guest molecules. The first guest is involved in a hydrogen bond and π-π interactions, while the second one is only involved in π-π interactions, which has not been observed in previous studies. The corresponding chirality transfer mechanism was also rationalized by DFT calculations.

Hydrogen bonds are very common and important interactions in biological systems, they are used to control the microenvironment around metal centers. It is a challenge to develop appropriate models for studying hydrogen bonds. We have synthesized two metal complexes of the phenol-tailed porphyrin, [Zn(HL)] and [Fe(HL)(C6H4(OH)(O))]. X-ray crystallography reveals that the porphyrin functions as a dianion HL2− and the phenol OH is involved in hydrogen bonds in both structures. In [Zn(HL)], an intramolecular hydrogen bond is formed between the carbonyl oxygen and OH. In [Fe(HL)(C6H4(OH)(O))], the unligated O(5) of the ligand is involved in two hydrogen bonds, as a hydrogen bond donor and a hydrogen bond acceptor. The overall electronic effect on the ligand could be very small, with negligible impact on the structure and the spin state of iron(III). The structural differences caused by the hydrogen bonds are also discussed.

A new host-guest system is formed between a benzene tricarboxamide linked zinc trisporphyrinate and a chiral monoalcohol (1-phenylethylalcohol). CD spectra show the chirality induction and inversion processes, which are controlled by the corresponding 1 : 1 and 1 : 2 coordination complexes. The binding constants calculated by UV-vis and CD spectral data are much larger than that for [Zn(TPP)] (TPP = tetraphenylporphyrin). The crystallographic structure of the host-guest complex reveals that multiple intramolecular hydrogen bonds and π-π interactions could contribute to its high binding affinity to 1-phenylethylalcohol. The DFT calculations suggest that the spatial orientations of porphyrin moieties change from the 1 : 1 complex to the 1 : 2 complex. The chirality induction and inversion processes are rationalized by the summation of pairwise interactions among multichromophores according to pairwise additivity.

A new covalent organic framework (COF), PP-TzDa, has been synthesized by post-synthetic modification. Our studies suggest that the modification leads to the changes of both the stacking mode and the fluorescence emission. This new COF shows dual fluorescence emissions, and can be used as a ratiometric fluorescent temperature sensor. In the range of 20–100 °C, the COF suspensions in DMF exhibit the temperature dependent fluorescence and the intensity ratios of two emissions change linearly with temperature. The new COF can also be used as a ratiometric fluorescent sensor for MnO4-. This work represents the opportunity to tune their fluorescent properties and explore their applications of a variety of COFs by simple modification.

We have designed and synthesized a new chiral zinc bisporphyrinate ([Zn2(D-BTABis)]) and investigated its enantioselectivity towards amino acid esters. Our studies reveal the binding of D-type of amino acid esters to this chiral zinc bisporphyrinate is more favorable than L-type of amino acid esters, the corresponding enantioselectivity (α) is 8.4 for the phenylalanine ethyl esters. NMR studies suggest these guests are monodentate ligands in the host-guest complexes. Further DFT calculations rationalize the CD results and enantioselectivity. When the chiral host interacts with the D-enantiomers of these guests, the steric repulsion interactions between the linker and the guest are weaker, and the tartaryl group adopts the conformation A with a larger positive torsion angle. These cause the complexes with D-type of amino acid esters are more energetically favorable than those with L-type of amino acid esters. Our studies provide one good bisporphyrin system for enantiodiscrimination of monodentate guests.

We have designed and synthesized a novel amide-linked bisporphyrin with a 2-naphthalenecarboxamide substituent on the linker. The chirality sensing ability of this zinc porphyrinate towards chiral monoamines has been examined. Circular dichroism studies indicate chirality transfer from chiral monoamines to the corresponding host-guest complexes. Interestingly, when optically pure 1-(1-naphthyl)ethylamine is used as a guest, stoichiometrically controlled chirality inversion occurs in the formation of the corresponding zinc bisporphyrinate-monoamine complexes. Both CD and NMR spectra indicate that 1 : 1 and 1 : 2 complexes are formed in solution. DFT calculations suggest that steric interactions between the substituent of the linker and the guest in the 1 : 2 complex are responsible for this unprecedented observation. Our studies provide a unique bisporphyrin system for demonstrating that chirality transfer to the host can be tuned by changing the substituent of the linker.

The influence of hydrogen binding to the N–H group of coordinated imidazole in high-spin iron(II) porphyrinates has been studied. The preparation and characterization of new complexes based on [Fe(TPP)(2-MeHIm)] (TPP is the dianion of tetraphenylporphyrin) are reported. The hydrogen bond acceptors are ethanol, tetramethylene sulfoxide, and 2-methylimidazole. The last acceptor, 2-MeHIm, was found in a crystalline complex with two [Fe(TPP)(2-MeHIm)] sites, only one of which has the 2-methylimidazole hydrogen bond acceptor. This latter complex has been studied by temperature-dependent Mossbauer spectroscopy. All new complexes have also been characterized by X-ray structure determinations. The Fe–NP and Fe–NIm bond lengths, and displacement of the Fe atom out of the porphyrin plane are similar to, but marginally different than, those in imidazole-ligated species with no hydrogen bond. All the structural and Mossbauer properties suggest that these new hydrogen-bonded species have the same electronic configurat...

m-Phthalic diamide-linked zinc bisporphyrinates have been developed as chirality probes for monoamines. They are capable of determining the absolute configuration of monoamines and distinguishing between alkyl and aryl substituents of chiral monoamines. Our studies suggest that steric interactions play critical roles in the molecular recognition process.

An m-phthalic diamide-linked bisporphyrin with a benzylamide substituent has been designed and synthesized. It has two types of carbonyl groups. In the solution of this zinc bisporphyrinate, these carbonyl groups are involved in the formation of two different Zn-O coordination interactions: one is formed between neighboring zinc bisporphyrinates; another is formed within zinc bisporphyrinate. The chirality sensing abilities of this zinc porphyrinate to a number of chiral monoamines have been examined. When zinc bisporphyrinate was mixed with a series of chiral monoamines, the signs of the circular dichroism spectra for the chiral monoamines of the same handedness with an aryl group as the substituent are just opposite to those with an alkyl group as the substituent. NMR studies reveal that stepwise coordinations lead to 1:1 and 1:2 host-guest complexes. The structure of the 1:1 host-guest complex was confirmed by crystallography, it is the first time that a 1:1 host-guest complex formed between zinc bisporphyrinate and a chiral monoamine has been crystallographically characterized. The structure reveals that there is an intramolecular hydrogen bond between the amide oxygen and the coordinated NH

Although the sophisticated Langmuir and Langmuir–Blodgett (LB) techniques facilitate the fabrication of uniform ultrathin monolayer and films, they are also revealed as powerful tools for the bottom–up construction of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked zinc bisporphyrinate tweezers using the Langmuir and LB techniques. It was found that the two tweezer-type zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates using the vertical lifting method. Atomic force microscopy (AFM) revealed that at the initial spreading stage, the compound formed flat disklike domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

A novel malonamide-linked zinc bisporphyrinate [Zn2-1] has been designed and synthesized. UV-vis and NMR spectroscopic studies suggest the molecule aggregates in solution. Such zinc bisporphyrinate is very CD-sensitive when it is mixed with amino acid ethyl esters. The amplitude value of the induced circular dichroism (ICD) is up to ca. 1500 L·mol−1·cm−1. Further studies by 1H NMR and UV-vis spectroscopies reveal amino acid esters function as monodentate ligands, and [Zn2-1] interacts with amino acid ethyl esters through coordination and hydrogen bonding interactions.

A monoamide-linked monozinc bisporphyrinate for monodentate chiral guests was designed and synthesized. It was used as a host to complex with amino acid esters; the resulting CD spectra showed typical bisignate shape, which suggest the ability to transfer chirality from amino acid esters. The molecular structure of the host indicates that amino acid esters function as monodentate ligands in the host-guest complex. 1H NMR spectroscopic studies suggest formation of a hydrogen bond between the amide NH and the carbonyl oxygen groups of the amino acid ester. The possible mechanism of the chiral induction process was further studied by DFT calculations.

The complete iron vibrational spectrum of the five-coordinate high-spin complex [Fe(OEP)(2-MeHIm)], where OEP = octaethylporphyrinato and 2-MeHIm = 2-methylimidazole, has been obtained by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS) data. Measurements have been made in three orthogonal directions, which provides quantitative information for all iron motion. These experimental data, buttressed by density functional theory (DFT) calculations, have been used to define the effects of the axial ligand orientation. Although the axial imidazole removes the degeneracy in the in-plane vibrations, the imidazole orientation does not appear to control the direction of the in-plane iron motion. This is in contrast to the effect of the imidazolate ligand, as defined by DFT calculations, which does have substantial effects on the direction of the in-plane iron motion. The axial NO ligand has been found to have the strongest orientational effect (Angew. Chem., Int. Ed., 2010, 49, 4400). Thus the strength of the directional properties are in the order NOimidazolateimidazole, consistent with the varying strength of the Fe-ligand bond.

We have synthesized three complexes of 5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin (ENTPP), [Cu(ENTPP)], [Ni(ENTPP), and [Fe(ENTPP)Cl]. X-ray crystallography reveals that copper and nickel species are four-coordinate, while the iron complex is five-coordinate. The porphyrin in all the three species maintains similar conformations, in which rotational hindrance makes the ester group at the 8-position of naphthyl lie above the porphyrin plane leading to axial chirality in the single molecule. However, only chiral crystals of [Cu(ENTPP)] were obtained by spontaneous resolution upon crystallization, while [Ni(ENTPP) and [Fe(ENTPP)Cl] were obtained as achiral crystals of racemic compounds. CD spectra have also confirmed the chirality of the crystalline samples. The origin of CD signals has also been discussed.

Using aldehydes with different substituents of the aryl groups, we have synthesized a series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group by one-pot reactions. Our studies suggest the steric property of substituents is the major factor to affect the reaction yields, the steric hindrance is unfavorable for such reaction. Compared with those para-substituted species, NMR studies of 2,6-substituted species show upfield shifts for their NH and ethyl protons, downfield shifts for their pyrrole protons, which is probably due to the decrease of porphyrin ring current. Three of them have been characterized by X-ray crystallography. Structures show that the ester group is hanging over the porphyrin plane, compound 3 and 4 have much different core conformations from compound 2, which is probably due to the π–π interactions in the solid state.

5-(8-Carboxy-1-naphthyl)-10, 5, 20-tritolyl porphyrin (H3CNTTP) and its iron(III) complexes, [Fe(CNTTP)]2 and [Fe(CNTTP)(N-MeIm)2], were synthesized and characterized. X-ray crystallography revealed that the carboxylate group is “hanging” over the porphyrin plane. The rigid framework makes the distance between the carboxylate oxygen and iron in the same porphyrin too long to form a coordination bond. On the other hand, the carboxylate group is not bulky enough to block the axial binding site. In the presence of OH–, the carboxylate oxygen is coordinated to iron in the symmetry-related unit, which led to the dimeric structure, [Fe(CNTTP)]2. In the presence of excess N-methylimidazole, a six-coordinate species, [Fe(CNTTP)(N-MeIm)2], was obtained. In such a structure, CH···O interactions between the carboxylate group and imidazole probably play an important role to determine the orientation of imidazole plane. Two imidazole planes have relative parallel orientation. For [Fe(CNTTP)(N-MeIm)2], 1H NMR shows pyrrole protons at the region –10 to –25 ppm. EPR shows rhombic spectrum. Those suggest [Fe(CNTTP)(N-MeIm)2] is a type II low-spin iron(III) porphyrinate.

The phenol-tailed porphyrin ligand, H3L was synthesized as a model compound for catalases. H3L and its corresponding iron complex [Fe(L)] were synthesized by using the precursor, 5-(8-ethoxycarbonyl-1-naphthyl)-10, 15, 20-triphenyl porphyrin (ENTPP). They were characterized by 1H NMR spectroscopy, mass spectrometry, X-ray crystallography, and cyclic voltammetry. All the results have confirmed that the phenol group is covalently attached to the porphyrin. In the iron complex, phenolate oxygen is coordinated to iron(III) as the fifth ligand, leading to the five-coordinate high-spin iron(III) species.

We have designed and synthesized a novel zinc trisporphyrinate with a benzene tricarboxamide as the linker. In the presence of a large excess of 1-phenylethylamine, single crystals of the corresponding 1:3 host–guest complex were obtained, which provide the crystallographic structure of a host–guest complex consisting of an achiral porphyrin and a chiral monoamine. The structure reveals the 1-phenylethylamines adopt the “inside” binding mode that is stabilized by intramolecular hydrogen bonds. The NH2 of the 1-phenylethylamine is involved in both coordination and hydrogen bonding interactions. Circular dichroism (CD) and ultraviolet–visible spectra revealed that the 1:3 host–guest complex is dominant in the presence of a large excess of 1-phenylethylamine. The crystal structure shows there are two diastereomers of the 1:3 host–guest complexes. Density functional theory and TDDFT calculations suggest that one of the diastereomers is more energetically favorable, which dominates the CD signals.

We have synthesised a chiral liquid crystal with a tolane unit that exhibits intense fluorescence in both solution and the solid states. The liquid crystal can form the enantiotropic twist-grain boundary A (TGBA*) and Blue II phases, and the helical pitch of the TGBA* phase decreases with an increasing temperature.

In the presence of Brønsted–Lowry acids (phenol or dry HCl), the acyl chloride, which was obtained by the reaction between 5-(8-carboxyl-1-naphthyl) −10,15,20-triphenyl-porphyrin (CNTPP) and oxalyl chloride, reacted with tetrahydrofuran and led to the 4-chlorobutyl ester, P1, as the result of the acylative cleavage. P1 and its zinc complex [ZnP1] have been characterized by 1H NMR. The structure of [ZnP1] was obtained by X-ray crystallography. Zinc is coordinated by four pyrrole nitrogens. The 8-position substituent, a 4-chlorobutyl ester group, lies above the porphyrin plane.

The four porphodimethene isomers, 5,10- and 5,15-disubstituted, have been synthesized in a one-pot reaction by the Lindsey protocol. Three of them have been characterized by X-ray crystallography. Structures show that two of them are 5,15-porphodimethenes: one is syn-equatorial, another is anti-configuration; the third one is 5,10-porphodimethene. In the 5,10-porphodimethene, the tripyrrane subunit remains planar conformation. 1H NMR and UV-vis spectra have also been characterized. Both spectra reveal remarkable difference between 5,10- and 5,15-disubstituted isomers.

We have synthesized zinc complexes of H2ENTPP (5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin) as a model to study hydrogen-bonding interactions. When water or methanol is a ligand, crystals of [Zn(ENTPP)(CH3OH)] or [Zn(ENTPP)(H2O)] · C6H5CH3 were obtained. In both structures, the ligand has hydrogen-bonding interactions, but in different patterns. In [Zn(ENTPP)(CH3OH)], the methanol oxygen and carboxylate oxygen in the naphthyl group form an intermolecular hydrogen bond. In [Zn(ENTPP)(H2O)] · C6H5CH3, there are two independent molecules A and B. In molecule B, there is an intramolecular hydrogen bond between the water oxygen and the carboxylate oxygen, while in molecule A, besides the intramolecular hydrogen bond, there is an intermolecular hydrogen bond between the water oxygen and the carboxylate oxygen. 1H NMR spectra suggest the binding of methanol or water to zinc are equilibrium processes in solution. Equilibrium constant has been determined by UV-Vis measurements, and it suggests the...

We have designed a porphyrin with a Schiff-base substituent as a model to study intramolecular hydrogen-bonding. The corresponding complex [Zn(SATPP)(CH3OH)] has been synthesized and characterized by X-ray crystallography, 1H NMR, and UV-Vis spectroscopy. The structure shows that there are three phenyl groups and one salicylideneaminophenyl group at the meso positions of the porphyrin, and the phenol oxygen is involved in double hydrogen bonds, one within the salicylideneaminophenyl and the other between coordinated methanol and phenol oxygen. 1H NMR spectra suggest that the binding of methanol to zinc is an equilibrium process in solution and the equilibrium constant has been determined by UV-Vis measurements. The intramolecular hydrogen bond stabilizes the structure, and the binding affinity increases 10 times over the corresponding TPP (TPP, dianion of meso-5,10,15,20-tetraphenylporphyrin).

5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin (ENTPP) has been synthesized in a one-pot reaction, and the corresponding chiral crystalline samples have been obtained by spontaneous resolution. 1 H NMR spectrum suggests it is mononaphthyl substituted species and an ethyl group is over the porphyrin plane. The structure has been further confirmed by X-ray crystallography. ENTPP·C6H14 (C57H50N4O2 ): monoclinic, P21, a = 10.707(2) Å, b = 12.203(2) Å, c = 17.858(4) Å, β = 103.06(3)°, V = 2272.8(8) Å3, Z = 2. The 8-position substituent, ester group, lies above the porphyrin plane and leads to the conformational chirality. The entire structure is built up with homochiral molecules, which leads to a chiral crystal through packing in P21 space group. Circular dichroism (CD) spectra have exhibited remarkable absorptions in the Soret band region, which further confirms the homochirality of the crystalline samples.