Homocarbaporphyrinoids: The m‐o‐m and p‐o‐p Terphenyl Embedded Expanded Porphyrin Analogues and Their Rh^I Complexes

Abstract

Stable homocarbaporphyrinoids were successfully synthesized by incorporating the m‐o‐m and p‐o‐p terphenyl units into the porphyrin core. The distinct bonding modes of terphenyl in the macrocycle generated two structural isomers with two and four carbon atoms in the macrocyclic environment. The core was utilized to stabilize the RhI ion. The spectral and structural analyses revealed that the restricted (m‐o‐m) and allowed (p‐o‐p) conjugation in the macrocyclic core provide overall non‐aromatic characteristics both to the free bases and their complexes.

Expandierte Carbaporphyrinoide

“…[139] Im Unterschied zu 145 ist 162 nichtaroma- Srinivasan und Mitarbeiter berichteten über die Synthese der beiden expandierten Carbaporphyrinoide 165 und 166 mit p-o-p-beziehungsweise m-o-m-Te rphenyl-Einheiten, die in das formale Homoporphyrin-Gerüst [140] 20 eingebunden sind (Schema 28). [141] Beide Makrocyclen zeigten im 1 H-NMR-Spektrum nichtaromatische Eigenschaften, die nach der Protonierung mit TFAo der der Koordination von Rh(CO) 2 beibehalten wurden (Abbildung 9).…”

Bis‐4,4′‐biphenyl Ring Embedded Octaphyrin with Three Distinct Conformational Structures

“…The Dd value of inner and outer biphenyl protons is 0.8 ppm, which clearly reveals the nonaromaticc haracter in 5 ( Figure S14). [9,10] Scheme1.Synthesis of 5 and 6.…”

“…Overall, the spectral analysiss uggests that the nonaromatic character in complex 6 is retained as such. [9,10] The structure of 5 was characterized by X-ray analysisa s shown in Figure 3a.T he compound crystallizes in at etragonal crystal lattice (space group P4 2 /n) and is located on crystallographic twofold axis. The deshielded NH signal as observed in the NMR spectral analysis of 5 is reflected in the X-ray crystal analysis, in which intramolecular hydrogen-bonding interactions were observedb etween the pyrrolic amine NH and the imine Nw ith ab ond length and angle of N1ÀH1··· N2/N1'À Chem.E ur.J.…”

“…As observed in the spectrala nalyses, the two Rh I ions are coordinated with the dipyrromethene units.T he geometry around the Rh I ions is square planar.T he bond lengthsi nR h1ÀN1, Rh1ÀN2, Rh2ÀN3 and Rh2ÀN4 are between 2.07(4)a nd 2.09(5) ;w here these values are comparablew ith those of 3b,a lbeit larger with respect to 4b. [9,10] The dihedral angles between the meanp lane of the biphenylene and the dipyrromethene units are 88.86(1) and 89.38(9)8,r espectively;a nd provide an unsymmetrical structurew ith as inglyt wisted conformation ( Figure 4b). One of the Rh I ions is protruded above the mean dipyrromethene plane with ad istance of 1.04(1) and the other located below with ad istance of 1.06(2) .T he distance between theseR h I ions is 10.327 (7) .T he crystal analyses reveal the following weak non-bonding interactions:( i) one of the CH (C5ÀH5/C46À H46) protons of the biphenylene units shows weak anagostictype interactions with the metal ions and with ab ond length of C5ÀH5···Rh1 and C46ÀH46··· Rh2 corresponding to 2.89(4) and 2.89(5) ,r espectively (Figure 4b); [11] and (ii)ani ntermolecular hydrogen-bonding interaction between one of the CH protons (C6ÀH6/C45ÀH45) of the biphenyleneu nits with the p-cloud of the other biphenylene unit with ab ond length and angle for C6ÀH6···Ph(p)1 of 2.95(1) and 143.65(3)8;a nd for C45ÀH45···Ph(p)2 of 2.89(2) and 146.59(4)8,r espectively.…”

“…For example, in the case of 5 an intense band is observed at 431 nm, whileaweak band appeared at 642 nm. Upon protonation (5·2H + + )a nd metal ion insertion (6), the colouro ft he solution changes from green to blue and the intense bands are blue-shifted, whereas the weak bands are redshifteda scompared to 5.Overall the observed spectral pattern and molar extinctionc oefficient values are comparable with those reported for 3, [9] which clearly indicates the nonaromatic character in 5, 5·2H + + and 6.…”