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 NH2. We further investigated the chirality transfer mechanism by density functional theory calculations. Our studies suggest that the interactions between the linker and guests in this bisporphyrin system are crucial in the chirality transfer process, and the nature of the bulkiest substituent of chiral monoamines makes a difference. For R-type guests, with an alkyl group, the steric repulsion makes the conformer A more energetically favorable, which leads to the anticlockwise twist and negative Cotton effect. However, with an aryl group, the π–π interaction makes the conformer B more energetically favorable, which leads to the clockwise twist and positive Cotton effect.

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.

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.

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.

A common structural motif in heme proteins is a five-coordinate species in which the iron is coordinated by a histidyl residue. The widely distributed heme proteins with this motif are essential for the well being of humans and other organisms. We detail the differences in molecular structures and physical properties of high-spin iron(II) porphyrin derivatives ligated by neutral imidazole, hydrogen bonded imidazole, and imidazolate or other anions. Two distinct (high spin) electronic states are observed that have differing d-orbital occupancies and discernibly different five-coordinate square-pyramidal coordination groups. The doubly occupied orbital in the imidazole species is a low symmetry orbital oblique to the heme plane whereas in the imidazolate species the doubly occupied orbital is a high symmetry orbital in the heme plane, i.e., the primary doubly-occupied d-orbital is different. Methods that can be used to classify a particular complex into one or the other state include X-ray structure determinations, high-field Mössbauer spectroscopy, vibrational spectroscopy, magnetic circular dichroism, and even-spin EPR spectroscopy. The possible functional significance of the ground state differences has not been established for heme proteins, but is likely found in the pathways for oxygen transport vs. oxygen utilization.

A novel m-phthalic diamide-linked zinc bisporphyrinate [Zn2-1] has been designed and synthesized. Its chiral crystalline samples have been spontaneously resolved by crystallization. Data for C48H29N5OZn follow: tetragonal, I41, a = 17.809(2) Å, b = 17.809(2) Å, c = 27.080(8) Å, V = 8589 (3) Å3, Z = 8. X-ray crystallography reveals the two porphyrin subunits are clockwise arranged in the solved structure. Each zinc atom is coordinated by four pyrrole nitrogens and the amide oxygen of the neighboring molecule. Through coordination bonds, it forms a helical chain with P configuration along the c axis. The overall crystal forms an unprecedented chiral bisporphyin coordination polymer. The chirality of the single crystals has been confirmed by CD spectroscopy. UV–vis and NMR spectroscopic studies suggested the molecule aggregates in solution. Such m-phthalic diamide-linked zinc bisporphyrinate shows a strong chiral recognition ability for amino acid ethyl esters. The amplitude value of the induced circular dichroism (ICD) (∼1900 cm–1 M–1) is around 10 times larger than the one observed for the oxalic amide-linked species (Dalton Trans. 2013, 42, 7651–7659). Further studies by 1H NMR and UV–vis spectroscopies have revealed amino acid esters function as monodentate ligands, and [Zn2-1] interacts with amino acid ethyl esters through coordination and hydrogen bonding interactions. The CD amplitude values have also shown dependence on the bulkiness of the side chain of amino acid esters. A possible chiral recognition mechanism has been proposed.

The effects of the deprotonation of coordinated imidazole on the vibrational dynamics of five-coordinate high-spin iron(II) porphyrinates have been investigated using nuclear resonance vibrational spectroscopy. Two complexes have been studied in detail with both powder and oriented single-crystal measurements. Changes in the vibrational spectra are clearly related to structural differences in the molecular structures that occur when imidazole is deprotonated. Most modes involving the simultaneous motion of iron and imidazolate are unresolved, but the one mode that is resolved is found at higher frequency in the imidazolates. These out-of-plane results are in accord with earlier resonance Raman studies of heme proteins. We also show the imidazole vs imidazolate differences in the in-plane vibrations that are not accessible to resonance Raman studies. The in-plane vibrations are at lower frequency in the imidazolate derivatives; the doming mode shifts are inconclusive. The stiffness, an experimentally determined force constant that averages the vibrational details to quantify the nearest-neighbor interactions, confirms that deprotonation inverts the relative strengths of axial and equatorial coordination.

A novel oxalic amide-linked bisporphyrinate 1 has been designed and synthesized, which shows chiral recognition ability for amino acid ethyl esters. The structure of complex 1·(D-Phe-OEt)(L-Phe-OEt) has been solved by X-ray crystallography. It reveals the following information: bisporphyrin unit adopts anti-configuration; compound 1 forms 1:2 complex with amino acid ethyl esters; one important hydrogen bond is formed between the coordinated nitrogen of amino acid ester and carbonyl oxygen in the amide group. The chiral recognition mechanism has been further investigated by UV-Vis spectra, 1H NMR and DFT/TDDFT calculations.

A type of porphyrin–chlorin heterodimers have been synthesized in a one-pot reaction, and their porphyrin and chlorin moieties are directly β,β′-linked through an sp3 carbon. These species have been characterized by mass spectroscopy, 1H NMR, X-ray crystallography, cyclic voltammetry, UV-vis and fluorescence spectroscopy.

Nuclear resonance vibrational spectra have been obtained for six five-coordinate imidazole-ligated iron(II) porphyrinates, [Fe(Por)(L)] (Por = tetraphenylporphyrinate, octaethylporphyrinate, tetratolylporphyrinate, or protoporphyrinate IX and L = 2-methylimidazole or 1,2-dimethylimidazole). Measurements have been made on both powder and oriented crystal samples. The spectra are dominated by strong signals around 200–300 cm–1. Although the in-plane and out-of-plane vibrations are seriously overlapped, oriented crystal spectra allow their deconvolution. Thus, oriented crystal experimental data, along with density functional theory (DFT) calculations, enable the assignment of key vibrations in the spectra. Molecular dynamics are also discussed. The nature of the Fe–NIm vibrations has been elaborated further than was possible from resonance Raman studies. Our study suggests that the Fe motions are coupled with the porphyrin core and peripheral groups motions. Both peripheral groups and their conformations have significant influence on the vibrational spectra (position and shape).

Pyrazole, a neutral nitrogen ligand and an isomer of imidazole, has been used as a fifth ligand to prepare two new species, [Fe(TPP)(Hdmpz)] and [Fe(Tp-OCH3PP)(Hdmpz)] (Hdmpz = 3,5-dimethylpyrazole), the first structurally characterized examples of five-coordinate iron(II) porphyrinates with a nonimidazole neutral ligand. Both complexes are characterized by X-ray crystallography, and structures show common features for five-coordinate iron(II) species, such as an expanded porphyrinato core, large equatorial Fe−Np bond distances, and a significant out-of-plane displacement of the iron(II) atom. The Fe−N(pyrazole) and Fe−Np bond distances are similar to those in imidazole-ligated species. These suggest that the coordination abilities to iron(II) for imidazole and pyrazole are very similar even though pyrazole is less basic than imidazole. Mössbauer studies reveal that [Fe(TPP)(Hdmpz)] has the same behavior as those of imidazole-ligated species, such as negative quadrupole splitting values and relative large asymmetry parameters. Both the structures and the Mössbauer spectra suggest pyrazole-ligated five-coordinate iron(II) porphyrinates have the same electronic configuration as imidazole-ligated species.

A type of porphyrin–chlorin heterodimers have been synthesized in a one-pot reaction, and their porphyrin and chlorin moieties are directly β,β′-linked through an sp3 carbon. These species have been characterized by mass spectroscopy, 1H NMR, X-ray crystallography, cyclic voltammetry, UV-vis and fluorescence spectroscopy.

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.

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.

A common structural motif in heme proteins is a five-coordinate species in which the iron is coordinated by a histidyl residue. The widely distributed heme proteins with this motif are essential for the well being of humans and other organisms. We detail the differences in molecular structures and physical properties of high-spin iron(II) porphyrin derivatives ligated by neutral imidazole, hydrogen bonded imidazole, and imidazolate or other anions. Two distinct (high spin) electronic states are observed that have differing d-orbital occupancies and discernibly different five-coordinate square-pyramidal coordination groups. The doubly occupied orbital in the imidazole species is a low symmetry orbital oblique to the heme plane whereas in the imidazolate species the doubly occupied orbital is a high symmetry orbital in the heme plane, i.e., the primary doubly-occupied d-orbital is different. Methods that can be used to classify a particular complex into one or the other state include X-ray structure determinations, high-field Mössbauer spectroscopy, vibrational spectroscopy, magnetic circular dichroism, and even-spin EPR spectroscopy. The possible functional significance of the ground state differences has not been established for heme proteins, but is likely found in the pathways for oxygen transport vs. oxygen utilization.

A novel oxalic amide-linked bisporphyrinate 1 has been designed and synthesized, which shows chiral recognition ability for amino acid ethyl esters. The structure of complex 1·(D-Phe-OEt)(L-Phe-OEt) has been solved by X-ray crystallography. It reveals the following information: bisporphyrin unit adopts anti-configuration; compound 1 forms 1:2 complex with amino acid ethyl esters; one important hydrogen bond is formed between the coordinated nitrogen of amino acid ester and carbonyl oxygen in the amide group. The chiral recognition mechanism has been further investigated by UV-Vis spectra, 1H NMR and DFT/TDDFT calculations.