Structural and spectroscopy studies of the zinc complex of p-hydroxyphenylporphyrin

Comparative study of the structural and vibroelectronic properties of porphyrin and its derivatives

Density functional theory (DFT and time-dependent-DFT (TD-DFT) were employed to investigate the vibroelectronic structural properties of porphyrin and some derivatives: unsubstituted porphyrin (TPyr), meso-tetraphenylporphyrin (TPP), meso-tetrakis(p-sulfonatophenyl)porphyrin (TSPP), protonated-TPyr (H₂TPyr), deuterated-H₂TPyr (D₄TPyr), protonated-TPP (H₂TPP) and deuterated-H₂TPP (D₄TPP), protonated TSPP (H₂TSPP), deuterated-H₂TSPP (D₄TSPP), dicationic TSPP (H₆TSPP) and deuterated-H₆TSPP (D₈TSPP). The possible internal conversion (IC) and intersystem crossing (ISC) processes of these compounds were investigated. Finally, the relaxed ground state potential energy surface (PES) (S₀), and singlet (S_n, n = 1–24) and triplet (T_n) excited state PESs of the TSPP molecule were calculated as function of the dihedral angle (C_α-C_m-C_ϕ-C(ph)) rotation. The results of the calculations indicated that while the meso-substitutions caused a significant shift in frequencies when the meso-carbons within the parent-porphine (or TPyr) are involved in the vibrational motion of molecules; the protonation of the N atoms at the porphine/porphyrin core causes a significant blue shift when the H on the N atoms within the pyrroline are dominantly involved in the vibrational motions. The deuteration of N atoms not only caused a red-shift in the frequencies of the corresponding peaks below 1600 cm⁻¹, but also produced new vibrational modes of frequencies in the 2565–2595 cm⁻¹ range caused by the N-D bond stretching. Similarly, the deuteration of O atoms within the sulfonato groups (-SO₃⁻) exhibited a new peak at around 2642 cm⁻¹ due to O-D bond stretching. The measured Raman spectrum of the H₂TSPP is assigned based on the predicted Raman spectra of the compounds studied here and measured Raman spectrum of the TPP (from our previous work). The IR spectrum is assigned based on our calculations and measured IR spectra obtained from the literature. The results of the TD-DFT calculations did not only indicate that the meso-substitution and protonation of the porphyrin bring about a significant read shift in the electronic transitions; but also provided a strong evidence for the IC from the Soret band to Q-bands beside possibility of the ISC process; its existence depend on the other excited state process such as much faster vibrational relaxation; the IC and etc. The ground state PES curve (S₀) of the ionic TSPP exhibited two minima at the dihedral angle (C_α-C_m-C_ϕ-C) of about 66° (corresponds to the lowest ground state) and 110° (corresponds to next energetically stable state or the local minima). The energy deference between these two minima is 0.0132 eV (or 106 cm⁻¹) and the highest potential energy barrier when undergoing from the lowest ground state to this local state is only 0.0219 eV (177 cm⁻¹; which is compatible with the thermal energy (kT) at 298 K is 207.2 cm⁻¹.

Isomorphous free-base, Ni(ii)- and Cu(ii)-5,10,15,20-tetra(4-hydroxyphenyl)porphyrin nitrobenzene hexasolvates with tetragonal 3D hydrogen-bonded network structures

The crystal structures of 5,10,15,20-tetra(4-hydroxyphenyl)-21,23H-porphyrin nitrobenzene hexasolvate (1), 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatonickel(ii) and -copper(ii)nitrobenzene hexasolvates (2and3) are described.

Structural and molecular characterization of meso-substituted zinc porphyrins: a DFT supported study

Structural parameters of a range of over 100 meso-substituted zinc porphyrins were reviewed and compared to show how far the nature of the functional group may affect the interatomic distances and bond angles within the porphyrin core. It was proved that even despite evident deformations of the molecular structure, involving twisting of the porphyrin's central plane, the coupled π-bonding system remains flexible and stable. DFT calculations were applied to a number of selected porphyrins representative for the reviewed compounds to emphasize the relevance of theoretical methods in structural investigations of complex macrocyclic molecular systems. Experimental and DFT-simulated IR spectral data were reported and analyzed in context of the individual molecular features introduced by the meso substituents into the porphyrin moiety base. Raw experimental spectral data, including ¹H- and ¹³C-NMR, UV-Vis, FTIR, XRD, and other relevant physicochemical details have been provided for a specially chosen reference zinc porphyrin functionalized by tert-butylphenyl groups.