Porphyrin Building Research Articles

Dynamic Assembly of Porphyrin Wires Trapped on a Highly Oriented Pyrolitic Graphite Surface

Carefully designed porphyrin building blocks assemble through selective imidazole binding in various solvents to form linear multiporphyrin objects. From a dynamic mixture of monomers, dimers, and oligomers, linear objects were observed on a highly oriented pyrolitic graphite (HOPG) surface. On the surface, the objects' morphology clearly depended on the solvent used for deposition and was modified upon heating.

Self-assembling porphyrins and phthalocyanines for photoinduced charge separation and charge transport

Large π-conjugated compounds are promising building blocks for organic thin-film electronics such as organic light-emitting diodes, organic field-effect transistors, and organic photovoltaics. Utilization of porphyrins and phthalocyanines for this purpose is highly fascinating because of their excellent electric, photophysical, and electrochemical properties as well as intense self-assembling abilities arising from π-π stacking interactions. This paper focuses on fundamental aspects of self-assembled structures that have been obtained from porphyrin and phthalocyanine building blocks and more complex composites for photoinduced charge separation and charge transport toward the potential applications to organic thin-film electronics.

Excitation energy migration in covalently linked perylene bisimide macrocycles

A series of acetylene-linked perylene bisimide (PBI) macrocycles 3a–d with various ring sizes from trimer to hexamer have been synthesised by a palladium-catalysed homocoupling reaction of perylene bisimide 1. Photophysical properties of these PBI macrocycles have been examined by steady-state absorption, fluorescence, fluorescence lifetime, fluorescence anisotropy decay, and transient absorption measurements. Both pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly related with the excitation energy migration processes within PBI macrocycles where the exciton-exciton annihilation time and the polarization anisotropy decay time are well described in terms of the Forster-type incoherent energy hopping model. Consequently, the excitation energy hopping times of macrocycles become slower and then saturated as the ring size increases. Nevertheless, the intrinsically large transition dipole moment of PBI leads to fast energy transfer processes as compared to other artificial light-harvesting complexes such as those constructed from porphyrin building blocks.

Recent advances in porphyrinic metal–organic frameworks: materials design, synthetic strategies, and emerging applications

This highlight presents a review of porphyrin paddlewheel frameworks (PPFs) created using porphyrin metalloligands and paddlewheel secondary building units. The combination of these two components, along with dipyridyl pillaring linkers, results in the assembly of 25 PPFs. We describe the topology control exhibited in this series by considering the preferred coordination geometry of the porphyrin building blocks, the length and steric effects of the pillars, and the use of sequential self-assembly. These PPFs and related porphyrinic metal–organic frameworks are emerging as important materials for applications such as heterogeneous catalysis, gas storage, and light harvesting.

Synthesis of functionalized core-modified sapphyrins and covalently linked porphyrin–sapphyrin dyads

We adopted simple synthetic strategy to synthesize mono-functionalized thiasapphyrins containing functionalized aryl group in the meso-position at thiophene side. The thiasapphyrin building block containing iodophenyl functional group was coupled with three different porphyrin building blocks with N 4, N 3S and N 2S 2 cores containing meso-ethynylphenyl functional group under mild Pd(0) coupling conditions to synthesize three covalently linked diphenyl ethyne bridged porphyrin–thiasapphyrin dyads. The porphyrin–thiasapphyrin dyads were characterized by mass, NMR, absorption, electrochemical and fluorescence techniques. The NMR, absorption and electrochemical studies indicated that the two components in dyads interact weakly and retain their individual identities. The steady state fluorescence studies indicated that the porphyrin fluorescence is reduced to a significant extent because of energy and/or electron transfer to the thiasapphyrin unit. The protonation studies indicated that N 4 porphyrin unit is more basic, whereas N 3S and N 2S 2 porphyrin units are less basic compared to thiasapphyrin unit in respective dyads. We explored the potential of dyads as fluorescent anion sensors and showed that two out of three dyads can be used as fluorescent anion sensors.

Synthesis of Mono‐Functionalized Core‐Modified Expanded Porphyrin Building Blocks and Covalently Linked Expanded Porphyrin Dyads

AbstractA series of mono‐functionalized core‐modified expanded porphyrin building blocks such as thiasapphyrin, thiarubyrin, oxasmaragdyrin, and BF2–oxasmaragdyrin have been synthesized by simple condensation of readily available precursors. The mono‐functionalized core‐modified expanded porphyrin building blocks were used to synthesize the first three examples of covalently linked diphenylethyne‐bridged dyads containing two different expanded porphyrin macrocycles, namely thaisapphyrin–BF2–oxasmaragdyrin, thiarubyrin–BF2–oxasmaragdyrin, and thiasapphyrin–thiarubyrin, by coupling appropriate mono‐functionalized expanded porphyrin building blocks under mild Pd0 coupling reaction conditions. The three dyads were freely soluble in common organic solvents and characterized by MS, NMR, absorption, electrochemical, and fluorescence techniques. The NMR, absorption, and electrochemical studies indicated that the two macrocycles in the dyads interact weakly with each other and maintain their independent characteristic features. The steady‐state fluorescence studies of the dyads showed that the thiasapphyrin and thiarubyrin units are nonfluorescent but fluorescence was observed from the BF2–oxasmaragdyrin unit. However, the quantum yield of the BF2–oxasmaragdyrin unit in the dyads was less than that of monomeric BF2–oxasmaragdyrin because of an enhancement of nonradiative decay channels operating in the dyads. The potential use of two of the three dyads containing the BF2–smaragdyrin subunit as fluorescent sensors for anions was explored. The studies showed that the binding of the anion at the protonated sapphyrin and rubyrin sites in the respective dyads can be followed by the clear changes in the fluorescence band of the BF2–oxasmaragdyrin unit, which indicates that these dyads can be used as fluorescent anion sensors.

Microscopic crystalline rods from the self-assembly of mixed porphyrin building blocks

Abstract Porphyrin based microscopic crystalline rods have been synthesized from mixed building blocks. Both pyridine and hydroxide are prerequisite functionalities to generate crystalline materials. Porphyrin building blocks containing just pyridyl or hydroxy groups do not interact themselves and the formation of amorphous solids is observed.

Hierarchical Self-Assembly of Superlattice Hybrids Consisting of Periodic and Alternating Cores of Porphyrin Molecules Separated by Nanoscale Silica Walls

Molecularly engineered superlattice hybrids consisting of periodic and alternating cores of porphyrin molecules separated by nanoscale silica walls were synthesized through a one-step organic-inorganic hierarchical self-assembly approach. The self-assembly process not only could lock both porphyrin and inorganic building blocks into ordered 3D nanostructure but also could allow for the molecular-level controllable organization of porphyrin molecules in the central regions of the silica pore channels, which leads to the formation of porphyrin core-silica wall superlattice hybrids with molecular-scale and mesoscale ordering. It was demonstrated that both the mesostructure and morphology of the hybrids can be finely tailored by turning the cooperative self-assembly process. It is significant that the hybrids show self-assembled optical properties consistent with the orientational arrangement of the porphyrins within periodic nanoscale silica channels. The methodology introduced herein demonstrates high versatility with respect to the self-assembly of optical active macrocycles into highly ordered superlattice hybrid architectures.

Versatile Molecular Recognition Features of Tetra(3-pyridyl)porphyrin in Crystal Engineering

This study explores the supramolecular reactivity of the meso-tetra(3-pyridyl)porphyrin (T3PyP) building block in the context of crystal engineering. This ligand has coordination as well as hydrogen bonding tetradentate functionalities and exhibits orientational versatility of the 3-pyridyl substituents. Reactions of the T3PyP with copper and manganese chlorides afforded hybrid coordination polymers with uniquely interesting and novel architectures of three-dimensional connectivity, in which the metal ions have multiple oxidation states. Several different modes of intermolecular association have been observed in crystalline adducts of T3PyP with various aqua nitrate salts of lanthanoid metal ions, which bear multiple molecular recognition sites on their nitrate and water ligands. The porphyrin component in these structures is characterized by differently protonated states. It is either interlinked through the inorganic connectors into self-assembled three-dimensional architectures or exhibits self-complem...

Synthesis of oligo( p-phenylene)-linked dyads containing free base, zinc(II) or thallium(III) porphyrins for studies in artificial photosynthesis

A series of ( p-phenylene) n -linked meso-mesityl-substituted porphyrin dyads ( n=2–4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers ( n=1–4), four other porphyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared.

ChemInform Abstract: New Effective Synthons for Supramolecular Self-Assembly of meso-Carboxyphenylporphyrins.

Tesselation of new supramolecular motifs of the tetra(4-carboxyphenyl)porphyrin building blocks by metal ion templates has been demonstrated in crystals, characterizing the square-planar [Na+·(–COOH)4·X− ] and the tetrahedral [Zn2+·(–COOH)2·(–COO −)2] molecular recognition elements for effective multiporphyrin assembly.

Versatile supramolecular reactivity of zinc-tetra(4-pyridyl)porphyrin in crystalline solids: Polymeric grids with zinc dichloride and hydrogen-bonded networks with mellitic acid.

Crystal engineering studies confirm that the zinc-tetra(4-pyridyl)porphyrin building block reveals versatile supramolecular chemistry. In this work, it was found to be reactive in the assembly of both (a) a 2D polymeric array by a unique combination of self-coordination and coordination through external zinc dichloride linkers and (b) an extended heteromolecular hydrogen-bonded network with mellitic acid sustained by multiple connectivity between the component species.

Square-grid coordination networks of (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) in its clathrate with two guest molecules of 1,2-dichlorobenzene: supramolecular isomerism of the porphyrin self-assembly

The title compound, (5,10,15,20-tetra-4-pyridylporphyrinato)zinc(II) 1,2-dichlorobenzene disolvate, [Zn(C(40)H(24)N(8))].2C(6)H(4)Cl(2), contains a clathrate-type structure. It is composed of two-dimensional square-grid coordination networks of the self-assembled porphyrin moiety, which are stacked one on top of the other in a parallel manner. The interporphyrin cavities of the overlapping networks combine into channel voids accommodated by the dichlorobenzene solvent. Molecules of the porphyrin complex are located on crystallographic inversion centres. The observed two-dimensional assembly mode of the porphyrin units represents a supramolecular isomer of the unique three-dimensional coordination frameworks of the same porphyrin building block observed earlier. The significance of this study lies in the discovery of an additional supramolecular isomer of the rarely observed structures of metalloporphyrins self-assembled directly into extended coordination polymers without the use of external ligand or metal ion auxiliaries.

Nanoporous Crystals of Calixarene/Porphyrin Supramolecular Complex Functionalized by Diffusion and Coordination of Metal Ions

A highly nanoporous material has been obtained by self-assembly of calixarene and porphyrin building blocks. This supramolecular zeolite-like structure was successively functionalized by diffusion and coordination of metal ions to form a new bifunctionalized nanoporous material containing a porphyrinic pigment together with a metal center.

Classification of Structural Motifs in Porphyrinic Coordination Polymers Assembled from Porphyrin Building Units, 5,10,15,20-Tetrapyridylporphyrin and Its Derivatives

In this review, we classify 1D, 2D, and 3D structural motifs found in porphyrinic coordination polymers assembled from 5,10,15,20-tetrapyridylporphyrin (TPyP) and its derivatives. The classifications are based on dimensionality, metal-to-porphyrin linkage, porphyrin type, and metal-to-porphyrin ratio. 1D porphyrin polymers often share the same connectivity (or structural motifs) with analogous 2D and 3D polymers. We identify interrelationships among 1D, 2D, and 3D coordination polymers and examine the connectivity of such interrelated structures. We also discuss the broad similarities and differences of the synthetic methods of all structures presented here. We classify 1D, 2D, and 3D structural motifs found in porphyrinic coordination polymers assembled from 5,10,15,20-tetrapyridylporphyrin (TPyP) and its derivatives. The classifications are based on dimensionality, metal-to-porphyrin linkage, porphyrin type, and metal-to-porphyrin ratio. We identify interrelationships among 1D, 2D, and 3D coordination polymers and examine the connectivity of such interrelated structures.

Synthesis of Covalently Linked Unsymmetrical Porphyrin Pentads Containing Three Different Porphyrin Subunits

The tetrafunctionalized AB3-type porphyrin building blocks containing two different types of functional groups with N4, N3O, N3S, and N2S2 porphyrin cores were synthesized by following various synthetic routes. The AB3-type tetrafunctionalized N4 porphyrin building block was synthesized by a mixed condensation approach, the N3S and N3O porphyrin building blocks by a mono-ol method, and N2S2 porphyrin building block by an unsymmetrical diol method. The tetrafunctionalized porphyrin building blocks were used to synthesize monofunctionalized porphyrin tetrads containing two different types of porphyrin subunits by coupling of 1 equiv of tetrafunctionalized N4, N3O, N3S, and N2S2 porphyrin building block with 3 equiv of monofunctionalized ZnN4 porphyrin building block under mild copper-free Pd(0) coupling conditions. The monofunctionalized porphyrin tetrads were used further to synthesize unsymmetrical porphyrin pentads containing three different types of porphyrin subunits by coupling 1 equiv of monofunctionalized porphyrin tetrad with 1 equiv of monofunctionalized N2S2 porphyrin building blocks under the same mild Pd(0) coupling conditions. The NMR, absorption, and electrochemical studies on porphyrin tetrads and porphyrin pentads indicated that the monomeric porphyrin subunits in tetrads and pentads retain their individual characteristic features and exhibit weak interaction among the porphyrin subunits. The steady state and time-resolved fluorescence studies support an efficient energy transfer from donor porphyrin subunit to acceptor porphyrin subunit in unsymmetrical porphyrin tetrads and porphyrin pentads.

Synthesis of Porphyrins Bearing Multiple meso-Aminoalkyl Groups

The design andsynthesis of basic porphyrin building blocks for the con-struction of highly ordered systems often require incorpo-ration of different peripheral substituents. The synthesis ofporphyrins bearing specific patterns of functionality is stillchallenging task in spite of the ample presence of reportedprocedure.

A General Method for Constructing Optically Active Supramolecular Assemblies from Intrinsically Achiral Water‐Insoluble Free‐Base Porphyrins

We have developed a general method to construct optically active porphyrin supramolecular assemblies by using a simple air-water interfacial assembly process. The method involved the in situ diprotonation of the free-base porphyrins at the air-water interface and subsequent assembly under compression. We showed that two intrinsically achiral water-insoluble free-base porphyrin derivatives, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (H(2)OEP) and 5,10,15,20-tetra-p-tolyl-21H,23H-porphine (H(2)TPPMe), could be diprotonated when spread onto a 2.4 M hydrochloric acid solution surface, and the Langmuir-Schaefer (LS) films fabricated from the subphase exhibited strong circular dichroism (CD) absorption, whereas those fabricated from pure Milli-Q water subphase did not. The experimental data suggested that the helical stacking of the achiral porphyrin building blocks was responsible for the supramolecular chirality of the assemblies. Interestingly, such a method was successfully applied to a series of other intrinsically achiral free-base porphyrins such as 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine (H(2)TPPOMe), 5,10,15,20-tetraphenyl-21H,23H-porphine (H(2)TPP), 5,10,15,20-tetrakis(4-(allyloxy)phenyl)-21H,23H-porphine (H(2)TPPOA), and 5,10,15,20-tetrakis(3,5-dimethoxyphenyl)-21H,23H-porphine (H(2)TPPDOMe). A possible mechanism has been proposed. The method provides a facile way to obtain optically active porphyrin supramolecular assemblies by using intrinsically achiral water-insoluble free-base porphyrin derivatives.

Nano-architectures by covalent assembly of molecular building blocks

The construction of electronic devices from single molecular building blocks, which possess certain functions such as switching or rectifying and are connected by atomic-scale wires on a supporting surface, is an essential goal of molecular electronics. A key challenge is the controlled assembly of molecules into desired architectures by strong, that is, covalent, intermolecular connections, enabling efficient electron transport between the molecules and providing high stability. However, no molecular networks on surfaces 'locked' by covalent interactions have been reported so far. Here, we show that such covalently bound molecular nanostructures can be formed on a gold surface upon thermal activation of porphyrin building blocks and their subsequent chemical reaction at predefined connection points. We demonstrate that the topology of these nanostructures can be precisely engineered by controlling the chemical structure of the building blocks. Our results represent a versatile route for future bottom-up construction of sophisticated electronic circuits and devices, based on individual functionalized molecules.

Porphyrin Framework Solids. Synthesis and Structure of Hybrid Coordination Polymers of Tetra(carboxyphenyl)porphyrins and Lanthanide-Bridging Ions

New types of porphyrin-based framework solids were constructed by reacting meso-tetra(3-carboxyphenyl)porphyrin and meso-tetra(4-carboxyphenyl)metalloporphyrins with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favorable hydrothermal reaction conditions, allowed the formation of open three-dimensional single-framework architectures by coordination polymerization, in which the tetradentate porphyrin units are intercoordinated by multinuclear assemblies of the bridging metal ions. The latter serve as construction pillars of the supramolecular arrays, affording stable structures. Several modes of coordination polymerization were revealed by single-crystal X-ray diffraction. They differ by the spatial functionality of the porphyrin building blocks, the coordination patterns of the lanthanide-carboxylate assemblies, and the topology of the resulting frameworks. The seven new reported structures exhibit periodically spaced 0.4-0.6 nm wide channel voids that perforate the respective crystalline polymeric architectures and are accessible to solvent components. Materials based on the m-carboxyphenyl derivative reveal smaller channels than those based on the p-carboxyphenyl analogues. An additional complex of the former with a smaller third-row transition metal (Co) is characterized by coordination connectivity in two dimensions only. Thermal and powder-diffraction analyses confirm the stability of the lanthanide-TmCPP (TmCPP=tetra(m-carboxyphenyl)porphyrin) frameworks.