Metal-mediated coordination polymer nanotubes of 5,10,15,20-tetrapyridylporphine and tris(4-pyridyl)-1,3,5-triazine at the water–chloroform interface

Metalloporphyrinic metal-organic frameworks: Controlled synthesis for catalytic applications in environmental and biological media

Recently, as a new sub-family of porous coordination polymers (PCPs), porphyrinic-MOFs (Porph-MOFs) with biomimetic features have been developed using porphyrin macrocycles as ligands and/or pillared linkers. The control over the coordination of the porphyrin ligand and its derivatives however remains a challenge for engineering new tunable Porph-MOF frameworks by self-assembly methods. The key challenges exist in the following respects: (i) collapse of the large open pores of Porph-MOFs during synthesis, (ii) deactivation of unsaturated metal-sites (UMCs) by axial coordination, and (iii) the tendency of both coordinated moieties (at peripheral meso- and beta-carbon sites) and the N₄-pyridine core to coordinate with metal cations. In this respect, this review covers the advances in the design of Porph-MOFs relative to their counterpart covalent organic frameworks (Porph-COFs). The potential utility of custom-designed porphyrin/metalloporphyrins ligands is highlighted. Synthesis strategies of Porph-MOFs are also illustrated with modular design of hybrid guest@host composites (either Porph@MOFs or guest@Porph-MOFs) with exceptional topologies and stability. This review summarizes the synergistic benefits of coordinated porphyrin ligands and functional guest molecules in Porph-MOF composites for enhanced catalytic performance in various redox applications. This review shed lights on the engineering of new tunable hetero-metals open active sites within (metallo)porphyrin-MOFs as out-of-the-box platforms for enhanced catalytic processes in chemical and biological media.

Amalgamating 4′-substituted 4,2′:6′,4′′-terpyridine ligands with double-helical chains or ladder-like networks

Hg^II-mediated self-assembly of metal–organic coordination polymers based on 4,2′:6′,4′′-terpyridine derivatives is for the first time presented and the structural diversity dependent upon the use of 4′-substituents of ligand is revealed.

A new and facile way to fabricate catalytically active block copolymer/Au nanoparticle multilayer thin films at the air/liquid interface

A catalytically active multilayer film of PB-b-P2VP doped with Au nanoparticles was fabricated through liquid/liquid interfacial mass transfer, self-assembly in an aqueous phase and adsorption at the air/liquid interface.

Synthesis, characterization and in vitro anticancer activity of the biomolecule-based coordination complex nanotubes

Biomolecule-based coordination complex nanoassemblies are a new type of functional materials that are attracting increasing attention. They could possess functionalities that are not readily attainable with other materials, and represent a promising research area that can be exploited in coordination chemistry and materials science. Using bioactive folic acid molecule as a linker, Ni-folate-hydrazine coordination complex nanotubes (CCNTs) have been effectively constructed using the solvothermal method. This is not only the first example of the CCNTs being formed using a nonpyridyl-based molecule as a linker, but also the first report on biomolecule-based CCNTs (BMB-CCNTs) with anticancer activity. It does not require any post treatment to achieve targeted delivery and biocompatible performance. The BMB-CCNTs are sufficiently stable at normal pH of 7.4 until it enters a tumor cell, subsequently it breaks open to release drug in the tumor cell. Furthermore, it overcomes the major limitations of antibody-drug and folate-drug conjugates and is a potential smart multi-functional nanomedicine system. The results of in vitro cytotoxicity assay reveal that the antitumor ability of BMB-CCNTs is similar to cisplatin (CDDP), while their cytotoxicity for normal cells is lower than the latter. Furthermore, BMB-CCNTs exhibit excellent performance as drug carriers and target agents for delivering drugs into tumor cells. Bio-TEM and confocal laser scanning microscope images trace the uptake process of CDDP-CCNTs by a tumor cell. CDDP-CCNTs exhibit dual anti-cancer effect.

Silver(I)-directed growth of metal-organic complex nanocrystals with bidentate ligands of hydroquinine anthraquinone-1,4-diyl diethers as linkers at the water-chloroform interface

Immiscible liquid-liquid interfaces provide unique double phase regions for the design and construction of nanoscale materials. Here, we reported Ag(I)-directed growth of metal-organic complex nanocrystals by using AgNO3 as a connector in the aqueous solution and bidentate ligand of 1,4-bis(9-O-dihydroquininyl)anthraquinone [(DHQ)2AQN] and its enantiomer of (DHQD)2AQN in the chloroform solutions as linkers. The Ag-(DHQ)2AQN and Ag-(DHQD)2AQN complex nanocrystals were formed at the liquid-liquid interfaces and characterized by using UV-vis absorption and fluorescence spectroscopy and X-ray photoelectron spectroscopy, as well as by using scanning electron microscopy. Screw-like nanocrystals were formed at the initial 30 min after the interfacial coordination reaction started, then they grew into nanorods after several days, and finally became cubic microcrystals after 2 weeks. The pure ligand showed two emission bands centered at about 363 and 522 nm in the methanol solution, the second one of which was quenched and shifted to about 470 nm in the Ag-complex nanocrystals. Two couples of reversible redox waves were recorded for the Ag-complex nanocrystals; one centered at about -0.25 V (vs. Ag/AgCl) was designated to one electron transfer process of Ag - (DHQ)2AQN and Ag - (DHQ)2AQN(+), and the other one centered at about 0.2 V was designated to one electron transfer process of Ag - (DHQ)2AQN and Ag(+) - (DHQ)2AQN.

Interfacial growth of large-area single-layer metal-organic framework nanosheets

The air/liquid interface is an excellent platform to assemble two-dimensional (2D) sheets of materials by enhancing spontaneous organizational features of the building components and encouraging large length scale in-plane growth. We have grown 2D molecularly-thin crystalline metal-organic-framework (MOF) nanosheets composed of porphyrin building units and metal-ion joints (NAFS-13) under operationally simple ambient conditions at the air/liquid interface. In-situ synchrotron X-ray diffraction studies of the formation process performed directly at the interface were employed to optimize the NAFS-13 growth protocol leading to the development of a post-injection method –post-injection of the metal connectors into the water subphase on whose surface the molecular building blocks are pre-oriented– which allowed us to achieve the formation of large-surface area morphologically-uniform preferentially-oriented single-layer nanosheets. The growth of such large-size high-quality sheets is of interest for the understanding of the fundamental physical/chemical properties associated with ultra-thin sheet-shaped materials and the realization of their use in applications.

Layer-by-layer assembly and characterization of multilayers of a manganese porphyrin linked poly(4-vinylpyridinium) derivative and poly(styrenesulfonic acid-o-maleic) acid

Multilayers of manganese(III) porphyrin-linked poly(vinylpyridinium) (MnTMPyP-PVPMe) polyelectrolyte and poly(styrenesulfonic acid-o-maleic) acid (PSS) have been assembled on gold, quartz, and indium tin oxide surfaces by a layer-by-layer (LBL) technique. The assembly process was monitored by measuring their absorption spectra and frequency change after each assembly, both of which confirmed the formation of three-dimensional MnTMPyP-PVPMe/PSS multilayers. The Soret absorption band of porphyrin red shifted about 8 nm in the multilayer compared with that in the dilute aqueous solution. The average mass changes for each assembly of MnTMPyP-PVPMe and PSS were estimated to be about 2.9 and 0.25 μg/cm(2), respectively. X-ray photoelectron spectra revealed that the as-prepared multilayers were composed of S 2p, C 1s, N 1s, O 1s, and Mn 2p, corresponding to polymers of MnTMPyP-PVPMe and PSS. A rough surface was observed after the assembly of MnTMPyP-PVPMe on the gold surface, but it became smoother when the PSS layer was adsorbed. The significant difference in the mass change and film morphology after the assembly of MnTMPyP-PVPMe compared to those after the assembly of PSS was ascribed to the reason that the MnTMPyP-PVPMe polyelectrolyte contained large metalloporphyrin macrocycles, which were axially coordinated to the pyridyl substituents of the PVP polymeric backbones. The cyclic voltammograms revealed two couples of redox waves in the phosphate electrolyte solution at pH 11, which corresponded to the electron-transfer processes of Mn(II)/Mn(III) and Mn(III)/Mn(IV) of polymeric manganese porphyrin MnTMPyP-PVPMe. The charge-transfer process was also investigated. Finally, the present MnTMPyP-PVPMe/PSS multilayers were used as a heterogeneous catalyst for the decoloration of an azo dye.

Interfacial self-assembly of metal-mediated viologen-like coordination polyelectrolyte hybrids of the bisterpyridine ligand and their optical, electrochemical, and electrochromic properties

Metal-mediated coordination polyelectrolyte multilayers with a bisterpyridine ligand (Bisterpy) have been self-assembled at air-water interfaces via coordination reactions of the bidentate ligand Bisterpy with inorganic salts in the subphases. To avoid dissolution of the viologen-like coordination polyelectrolyte monolayers, anionic poly(styrenesulfonic acid-o-maleic) (PSS) acid was added in the subphases as a supporting layer. The average molecular area of the ligand Bisterpy could reach 1.2-1.5 nm(2) on the surfaces of the subphases containing mixtures of inorganic salts (M) and PSS, although the ligand was unable to form a stable monolayer on the pure water surface. The Langmuir-Blodgett (LB) method was used to deposit the Bisterpy/PSS and M-Bisterpy/PSS hybrid multilayers on the substrate surfaces, which were characterized by using absorption and fluorescence spectroscopy as well as electrochemical analysis. Quasi-reversible redox waves were recorded and centered at about -0.68 and -0.92 V (vs Ag/AgCl), respectively, corresponding to the two-electron process of the ligand, Bisterpy2+ <--> Bisterpy(*+) <--> Bisterpy(0), which were slightly shifted to lower potentials in the LB films of metal-mediated coordination polymers. The film compositions were determined by using X-ray photoelectron spectroscopy. The as-prepared LB films showed strong stability and good electrochromic response upon the applied potential of -1.1 V vs Ag/AgCl and thus could act as potential materials in the development of redox-based molecular switches and display devices.

Self-organized porphyrinic materials

The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices.

Electrochemically driven generation of manganese(IV,V)-oxo multiporphyrin arrays and their redox properties with manganese(III) species in Langmuir-Blodgett films

High-valency manganese (IV,V)-oxo porphyrins have been electrochemically generated and in situ spectrally characterized in multiporphyrin arrays, which were formed by an interfacial coordination reaction of Na2PdCl4 with manganese (III) tetrapyridylporphyrin (MnTPyP). Multilayers of the Pd-MnTPyP multiporphyrin arrays were obtained by the Langmuir-Blodgett (LB) method. The redox behaviors of manganese in the multiporphyrin arrays were pH-dependent. Spectroelectrochemical experiments revealed a reversible redox process between Pd-Mn(III)TPyP and its Mn(IV)-oxo species, but an irreversible process between Pd-Mn(III)TPyP and its Mn(V)-oxo species. The Pd-Mn(IV)TPyP multiporphyrin arrays could be spontaneously reduced to their Mn(III) complex, while the Pd-Mn(V)TPyP arrays were rather stable in basic solutions (pH > 10.5). However, when the Pd-Mn(V)TPyP multiporphyrin arrays were washed by or immersed in water, they were immediately reduced to their Mn(III) complex. Because these well-organized multiporphyrin arrays are of high thermal and chemical stability, they are potential molecular materials in the studies of natural and artificial catalytic processes as well as redox-based molecular switches.

Sonication-assisted supramolecular nanorods of meso-diaryl-substituted porphyrins

Supramolecular nanorods of 5,15-diaryl-substituted porphyrins prepared by sonication method exhibit a broad absorption property, which is confirmed by photocurrent generation measurement in a photoelectrochemical cell.

Metal-cation-mediated nanocrystal arrays of sandwich-type (phthalocyaninato) [tetrakis(4-pyridyl)porphyrinato] cerium complex formed at the water–chloroform interface

Regular square, wirelike, quadrate, and rodlike nanocrystal arrays of Cd2+, Hg2+, or Ag+ metal-cation-mediated sandwich-type mixed (phthalocyaninato) [5,10,15,20-tetrakis(4-pyridyl)poprhyrinato] cerium(III) double-decker complex Ce(Pc)(TPyP) have been successfully prepared at the water-chloroform interface. The nanocrystal growth processes were monitored by transmission electron microscopy (TEM), which reveals that different morphologies of nanocrystals have been fabricated from double-decker molecules connected by different kinds of metal cations, forming coordination polymers. These nanoscaled coordination polymers were characterized by FT-IR spectra and energy-dispersive X-ray spectra (EDS). EDS results clearly revealed the elements of the nanocrystals and the FT-IR spectra give evidence for the coordination interaction between the double-decker molecules and metal cations. The UV-vis absorption spectrum indicates the formation of J-aggregates of the double-decker molecules in the nanocrystals formed.