Porphine molecule

Figure 32-1. The porphin molecule. Rings are labeled I, II, III, and IV. Substituent positions on the rings are labeled 1,2,3,4,5,6,7, and 8. The methenyl bridges (—HC=) are labeled a, (3,y, and 5.

Fig. 8.6. The porphin molecule. The NH hydrogen atoms are readily removed as protons and the resulting dianion acts as a quadridentate ligand.

Simplified structures of the porphine molecule and the Fe porphyrin complex. The dashed lines represent coordinate covalent bonds. 

The porphine molecule forms an important part of the hemoglobin structure. Upon coordination to a metal, the H ions that are bonded to two of the four nitrogen atoms in porphine are displaced. Complexes... 

Among the most important chelating agents in nature are those derived from the porphine molecule ( FIGURE 23.13). This molecule can coordinate to a metal via its four nitrogen donor atoms. Once porphine bonds to a metal ion, the two H atoms on the nitrogens are displaced to form complexes called porphyrins. Two important porphyrins are hemes, in which the metal ion is Fe(ll), and chlorophylls, with a Mg(ll) central ion. 

Gladkov, L.L. and K.N. Solovyov (1985). The normal coordinate analysis of porphin and its derivatives based on the solution of the inverse spectral problem for porphin and Cu porphin—II. A valence force field for in-plane vibrations of the Cu porphin molecule. Spectrochim. Acta A 41, 1443. 

A Figure 24.10 Structure of the porphine molecule. This molecule forms a trtradentate ligand with the loss of the two protons bound to nitrogen atoms. Porphine is the basic component of porphyrins, complexes that play a variety of important roles in nature. 

Fig. 4.4 Stacked dimers of a bisacetylacetonato metal-complexes 4 (M = Pt(II), Pd(II), and Cu(ll)) and b metal-porphine molecules (M = Cu(II)) within coordination host 1. c Triple stacks of metal-azaporphine molecules within box-shaped host 5 and d X-ray crystal structure of 5 D (6)3 (M = H2). e ESR spectra of 5 D (6)3 (M = Cu(II)) at 103 K...

Scheme 4.49. Use of its homolog without such substituents afforded the mixture of homotopic M4L4 square-planar metallomacrocycle and octahedral MgL 4 cage complex. The caging ligand 552 is also able to encapsulate a cofacial stacked por-phine dimer forming a 1 2 cage complex by Scheme 4.50 its extended analog 553 is described in [50] to give a heteroguest 1 2 1 compound with triple-decker encapsulated species containing two cofacial porphine molecules that sandwich one tris-pyridyl aromatic syntone 241 (Scheme 4.50).

The singlet-triplet transition moments and phosphorescence lifetimes were calculated by time-dependent density functions theory utilizing quadratic response (QR) functions the DFT QR method is described in Ref [32]. Besides the first excited triplet state (T ) of the free-base porphin molecule, which has nature, the second excited (T2) state is also smdied in order to understand the reasons for correlations of phosphorescence and microwave signals. The rate constant of spontaneous phosphorescence emission T" from a spin-sublevel (a) is determined by equation ... 

One has to note that the choice of z-axis, which determines the ZFS parameters D and E, depends on the molecule and on the symmetry of the triplet state. In our calculations of the free-base porphin molecule z-axis is along the N-H bonds and X-axis is out of plane. Numeration of atoms and orientation of axes is shown in Fig. 1.1. In that case, as follows from the present and from previous calculations [7, 28], Disnot determined by Eq. (1.5), but by D = — X, something that coincides with experimental findings [28], The ZFS tensor can be obtained by contracting two-electron field gradient integrals with a quintet two-electron density [47]... 

Normally, for the triplet state of organic molecules the ZFS parameters can be entirely determined as the SSC expectation value [48, 60]. But for the inr states in porphin the second-order SOC effect can produce an appreciable contribution to the ZFS since the FBP molecule has lone pairs at nitrogen atoms. We have therefore computed the 7i state of free-base porphin molecules taking into account both SSC and SOC perturbations. The SSC expectation values are calculated here by the singledeterminant SCF method for the high spin open shell [47] using Dalton code. 

Table 1.7 DFT calculated bond lengths A and bond angles (°) for the ground and triplet excited state of free-base porphin molecule ...

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