Energetics of Saddling versus Ruffling in Metalloporphyrins: Unusual Ruffled Dodecasubstituted Porphyrins

Abstract

Presented herein is a first major density functional theory (BP86/D3/STO-TZ2P) survey of the energetics of saddling versus ruffling for a wide range of dodecasubstituted metalloporphyrins with M = Ni, Cu, Zn, Pd, and Pt. For the majority of X 8 TPP (i.e., β-octasubstituted- meso -tetraphenylporphyrin), the calculations indicated a clear preference for the saddled conformation, consistent with a large body of experimental data. The preference for the saddled conformation relative to the ruffled conformation was found to vary from about ∼0.3–0.4 eV for Me 8 TPP derivatives up to 1 eV for I 8 TPP and (CF 3 ) 8 TPP derivatives. For X = Ph, that is, dodecaphenylporphyrins, the saddled and the ruffled conformation are almost equienergetic, with even a slight preference for the ruffled conformation in some cases. This finding provides a satisfactory explanation for the X-ray crystallographic observation of both saddled and ruffled conformations for dodecaphenylporphyrin complexes as well as for spectroscopic evidence for conformational mobility of these complexes in solution. The calculations also indicate near-equienergetic saddled and ruffled conformations for meso -tetraacetylenyltetrabenzoporphyrins, again consonant with key crystallographic findings. By and large, both the energetics and nonplanar distortions of the metalloporphyrin derivatives correlated well with the Charton and Sterimol B 1 steric parameters of the peripheral substituents.

Supramolecular Chirogenesis in Bis-Porphyrin: Crystallographic Structure and CD Spectra for a Complex with a Chiral Guanidine Derivative

“…Computational details. Structural optimization was performed using resolution of identity (RI) approximation [48][49][50], PB86 functional [51,52] with D3 dispersion correction [53] and def2-SV(P) basis set [54] implemented in Turbomole 7.0 [55], which showed good agreement with experimental data [56][57][58], as in a gas phase and in solvent. To include solvent effect the COSMO solvent model [59] was used.…”

One A3B Porphyrin Structure—Three Successful Applications

“…In addition, due to the fact that recent reports concluded that the Q(0,0), as well as the Soret band, has maximum intensity in the meta isomer and decreases in the series meta > para > ortho , and structural modification with meta substitution also increases antibacterial properties [ 53 ], the second decision was made to obtain an A 3 B porphyrin with all substituents in a meta position. The third guiding thought was that metalloporphyrins adopt various intermediate conformations besides the four main nonplanar conformations, namely: ruffled, saddled, domed and waved [ 54 ], and that although the hydroxyl group is generally electron donating, when it is in a meta position, it behaves as an electron-withdrawing group. The methoxy groups are also electron withdrawing by the inductive effect of the oxygen atom if they are in the meta position.…”

Distorted Phthalocyanines by Click Chemistry: Photoacoustic, Photothermal, and Surface‐Enhanced Resonance Raman Studies

“…Steric energy MM2 minimizations using Chembiodraw 3D support mixtures of nonplanar saddled and ruffled distortions after the first tomamine addition and that the di‐, tri‐, and tetratomamine compounds are only slightly more distorted . The exocyclic seven‐membered ring contributes about 26 kJ mol −1 of strain and the ionic radius of the Zn II ion causes it to sit out of the Pc plane thereby diminishing the rigidity and lowering the energy barriers to distortions of the macrocycle …”

“…Compared to the planar derivatives, distorted Pc have unique photophysical attributes such as near IR (NIR) absorption, low fluorescence and 1 O 2 quantum yields, solvent dependency, different redox potentials, distinct catalytic cycles, and diverse materials properties . Most Pc distortion is achieved by steric crowding of the peripheral substituents, especially at neighboring α,α‐positions . To develop a lipophilic or amphipathic Pc derivative, we substituted a commercial surfactant, isodecyloxypropyl‐1,3‐diamino‐propane (tomamine®), onto ZnF 16 Pc via a simple one‐step annulation to yield a seven‐membered ring on adjacent β‐positions of an isoindole (Scheme ).…”