Morphology-Controlled Self-Assembled Nanostructures of 5,15-Di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin Derivatives. Effect of Metal−Ligand Coordination Bonding on Tuning the Intermolecular Interaction

Abstract

Novel metal-free 5,15-di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin H2[DP(CH3COSC5H10O)2P] (1) and its zinc congener Zn[DP(CH3COSC5H10O)2P] (2) were designed and synthesized. Single-crystal X-ray diffraction (XRD) analysis confirmed the tetrapyrrole nature of these two compounds, revealing the existence of metal-ligand coordination bond between the carbonyl oxygen in the aryloxy side chain of meso-attached phenyl group in the porphyrin molecule with the zinc center of neighboring porphyrin molecule in the crystal structure of 2. This intermolecular Zn-O coordination bond induces the formation of a supramolecular chain structure in which the porphyrinato zinc moieties are arranged in a "head-to-tail" mode (J-aggregate), which is in contrast to a "face-to-face" stacking mode (H-aggregate) in the supramolecular structure formed depending on the C-H...pi interaction in the crystal of 1. Their self-assembling properties in MeOH and n-hexane were comparatively investigated by scanning electronic microscopy and XRD technique. Intermolecular pi-pi interaction of metal-free porphyrin 1 leads to the formation of hollow nanospheres and nanoribbons in MeOH and n-hexane, respectively. In contrast, introduction of additional Zn-O coordination bond for porphyrinato zinc complex 2 induces competition with intermolecular pi-pi interaction, resulting in nanostructures with nanorod and hollow nanosphere morphology in MeOH and n-hexane. The IR and XRD results clearly reveal the presence and absence of such metal-ligand coordination bond in the nanostructures formed from porphyrinato zinc complex 2 and metal-free porphyrin 1, respectively, which is further unambiguously confirmed by the single-crystal XRD analysis result for both compounds. Electronic absorption spectroscopic data on the self-assembled nanostructures reveal the H-aggregate nature in the hollow nanospheres and nanoribbons formed from metal-free porphyrin 1 due to the pi-pi intermolecular interaction between porphyrin molecules and J-aggregate nature in the nanorods and hollow nanospheres of 2 depending on the dominant metal-ligand coordination bonding interaction among the porphyrinato zinc molecules. The present result appears to represent the first effort toward controlling and tuning the morphology of self-assembled nanostructures of porphyrin derivatives via molecular design and synthesis through introduction of metal-ligand coordination bonding interaction. Nevertheless, availability of single crystal and molecular structure revealed by XRD analysis for both porphyrin derivatives renders it possible to investigate the formation mechanism as well as the molecular packing conformation of self-assembled nanostructures of these typical organic building blocks with large conjugated system in a more confirmed manner.

Structures and properties of novel 5,15-di[4-(5-acetylsulfanylpentyloxy)phenyl] porphyrin derivatives: Density functional theory calculations

“…Table S2 (Supporting Information) compares the calculated molecular structures of 1 and 2 with those obtained by single crystal X-ray analysis [22]. As can be seen, the calculated results for 1 and 2 correspond well with those obtained experimentally.…”

“…The initial input structures of 1 and 2 were obtained from single crystal X-ray diffraction analysis [22]. The structure of 2 in chloroform was also calculated by means of the integral equation formalism-polarizable continuum model (IEF-PCM), which can perform equally as well as, if not better than, the conducting polarized continuum model (CPCM) and isodensity surface polarized continuum model (IPCM) with lower cost [36].…”

“…Their physicochemical and spectroscopic properties have been revealed to be closely related not only to the nature and position of any substituents on the porphyrin macrocycle but also to the metal center [16][17][18][19][20][21]. Our group has just described the design, synthesis, single crystal structure, and self-assembly properties of two novel 5,15-di [4-(5- [22]. These two molecules have novel structures with two 5-acetylsulfanylpentyloxy side chains at the para-positions of opposite meso-attached phenyl groups and exhibit controlled self-assembly properties with different morphology in MeOH and n-hexane.…”

Structures and properties of 1,8,15,22-tetrasubstituted phthalocyaninato zinc and nickel complexes: Substitution and axially coordination effects study based on density functional theory calculations

“…However, the two hydrogen atoms of the water molecule may form two hydrogen bonds with the electron-abundant oxygen and nitrogen atom from another molecule of 4, which, in fact, has been proven true by single crystal X-ray structure analysis [32]. In addition, though very slight, the non-planarity of molecule 2 is very important for the two 2 molecules to form the dimeric supramolecular structure via the H 2 O-involved hydrogen bonding interaction instead of forming a one-dimensional chain by coordinating two H 2 O molecules, as in the 5,15-Di[4-(5-acetylsulfanylpentyloxy)phenyl]porphyrin zinc crystal [42]. In other words, forming the novel dimeric supramolecular structure {Zn[Pc(␣-OC 5 H 11 ) 4 ]·H 2 O} 2 from two molecules of 1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato zinc complex requires bulky non-peripheral substituents, which induces the non-planarity of the phthalocyaninato zinc molecule and therefore ensures the five coordination of the zinc ion rather than traditional six coordination.…”

Organic Nanostructures with Controllable Morphology Fabricated from Ferrocene–Porphyrin Derivatives: Effect of Metal–Ligand Coordination on the Morphology, Dimensions, and Semiconductor Properties of Self‐Assembled Nanostructures

“…In contrast, introduction of an additional Zn-O coordination bond in Zn[DP(CH 3 COSC 5 H 10 O) 2 P] induces competition with the intermolecular π-π interaction, resulting in nanostructures with nanorod and hollow nanosphere morphologies in MeOH and n-hexane. [11] Synergistic interplay of the original π-π interaction with metal-ligand coordination or hydrogen bonding interactions has also been revealed to successfully tune the morphology of self-assembled nanostructures of porphyrin derivatives. [12] For their unique physicochemical properties, ferrocenyl moieties have been introduced on to porphyrin rings using various strategies.…”