Competition of Major Forces Dominating the Structures of Porphyrin Assembly

Abstract

Here we take the self-assembly of porphyrin molecules as an example to discover the reason for the diversity of assembled structures. The self-assembly is conducted at a range of pH conditions. Irregular, tubular, and rodlike particles are formed at pH 1.5, 6.5 and 12.5, respectively. X-ray diffraction spectra and UV absorption show that these particles have the same crystalline structures, while the packing types of molecules are different. At low pH, the molecules assemble together by end to end attachment with a J-type aggregation, forming irregular particles. This assembly is dominated by the competition of π−π interaction and repulsion force. The latter force is induced by the protonation of molecules under acid conditions. With the increase of pH, the repulsion force is attenuated and finally disappears under basic conditions. The π−π interaction becomes the major force under basic conditions, leading to a H-type aggregation via face to face attachment and forming rodlike particles. At the middle pH, the competition disturbs the symmetry of molecules assembly, forming tubular particles. Together with previous studies, we expect that the compromise between competing interactions is probably the governing rule for the diversity of assembled structures.

A Functionalized Tetrakis(4-Nitrophenyl)Porphyrin Film Optical Waveguide Sensor for Detection of H2S and Ethanediamine Gases

“…On the other hand, the B band becomes red shifted, from 424 to 455 nm ( Figure 6 b), when the solution is exposed to H 2 S, and the four Q bands strengthen and merge into a single band. These spectral changes are observed both in solution, and in the solid film, and are in agreement with reports in the literature [ 55 ]. The red shift of the Soret band and the enhancement of the Q band at 659 nm indicate that the inner nitrogen atoms of the TNPP ring become protonated by H 2 S, leading to enhanced porphyrin conjugation and an overall reduction in the energy of the porphyrin system.…”

Adsorption, Ordering, and Metalation of Porphyrins on MgO Nanocube Surfaces: The Directional Role of Carboxylic Anchoring Groups

“…The rational development of functional hybrids connects to another key aspect in the utilization of porphyrins, namely, to their organization in supramolecular nanostructures . Diverse shapes of assembled porphyrin particles can be adjusted just by the solvent composition . The surfactant-assisted hierarchical self-assembly involving oil–water interfaces can be used to generate a variety of nanostructures, including hollow nanospheres, solid nanospheres, nanotubes, nanorods, and nanofibers. , While these approaches are performed in homogeneous liquid phase, the controlled assembly of porphyrins on high surface area materials such as nanoparticle networks or monolithic porous solids opens an important opportunity to prepare well-defined nanohybrids with 2D crystal phases or crystalline porphyrin nanofilms. , …”

Ultralarge Nanosheets Fabricated by the Hierarchical Self‐Assembly of Porphyrin‐Ended Hyperbranched Poly (ether amine) (TPP–hPEA)

“…As shown in Figure , in pure CHCl 3 , the major peak at 420 nm is assigned to the HBP1 molecules. With an increasing methanol content, the absorbance at 420 nm decreases remarkably (Figure a), which suggests that H‐type aggregation occurs between the porphyrin moieties (Figure ) . The slight blueshifted bands of the porphyrin moiety can further confirm that π–π interactions play a critical role in the aggregation of the porphyrin moieties .…”