One-dimensional (1D) coordination polymers (CPs) experiences limitations in exfoliation into individual strands, which hamper their utility as functional 1D nanomaterials. Here we synthesize chiral 1D-CPs that feature the bis(dipyrrinato)zinc(II) complex motif. They can be exfoliated into single strands upon sonication in organic media, retaining lengths of up to 3.19 μm (ca. 2600 monomer units). Their chiroptical structure allows the exfoliated wires to show circularly polarized luminescence at an intensity 5.9 times that of reference monomer complexes.

Photoluminescent coordination nanosheets (CONASHs) comprising three-way terpyridine (tpy) ligands and zinc(II) ions are created by allowing the two constitutive components to react with each other at a liquid/liquid interface. Taking advantage of bottom-up CONASHs, or flexibility in organic ligand design and coordination modes, we demonstrate the diversity of the tpy-zinc(II) CONASH in structures and photofunctions. A combination of 1,3,5-tris[4-(4′-2,2′:6′,2″-terpyridyl)phenyl]benzene (1) and Zn(BF4)2 affords a cationic CONASH featuring the bis(tpy)Zn complex motif (1-Zn), while substitution of the zinc source with ZnSO4 realizes a charge-neutral CONASH with the [Zn2(μ-O2SO2)2(tpy)2] motif [1-Zn2(SO4)2]. The difference stems from the use of noncoordinating (BF4–) or coordinating and bridging (SO42–) anions. The change in the coordination mode alters the luminescence (480 nm blue in 1-Zn; 552 nm yellow in 1-Zn2(SO4)2). The photophysical property also differs in that 1-Zn2(SO4)2 shows solvatoluminochromism, whereas 1-Zn does not. Photoluminescence is also modulated by the tpy ligand structure. 2-Zn contains triarylamine-centered terpyridine ligand 2 and features the bis(tpy)Zn motif; its emission is substantially red-shifted (590 nm orange) compared with that of 1-Zn. CONASHs 1-Zn and 2-Zn possess cationic nanosheet frameworks with counteranions (BF4–), and thereby feature anion exchange capacities. Indeed, anionic xanthene dyes were taken up by these nanosheets, which undergo quasi-quantitative exciton migration from the host CONASH. This series of studies shows tpy-zinc(II) CONASHs as promising potential photofunctional nanomaterials.

The authors create a zinc(II) complex featuring a simple chemical structure but multi-functional luminochromism. Reversible dissociation/association between the zinc center and the terpyridine ligand plays a key role in the multi-functional luminochromism.

The titled complex exhibits multi-functional luminochromism in the solid state, despite its simple chemical structure. The complex shows solid-state vapochromism and mechanochromism. The polymer analogue of the complex undergoes solvatochromism and thermochromism.

Imine-linked BODIPY oligomers show fluorescence quantum yields of up to 0.93. The azine linker may mediate π-conjugation that extends over six BODIPY units with redshifts up to 125 nm. BODIPYs are immobilized on silica gel through heterogeneous imine-bond formation, being fluorescent and robust.

Bis(dipyrrinato)metal(II) and tris(dipyrrinato)metal(III) complexes have been regarded as much less useful luminophores than their boron difluoride counterparts (4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes, BODIPYs), especially in polar solvent. We proposed previously that dissymmetry in such metal complexes (i.e., two different dipyrrinato ligands in one molecule) improves their fluorescence quantum efficiencies. In this work, we demonstrate the universality and utility of our methodology by synthesizing eight new dissymmetric bis(dipyrrinato)zinc(II) complexes and comparing them with corresponding symmetric complexes. Single-crystal X-ray diffraction analysis, 1H and 13C NMR spectroscopy, and high-resolution mass spectrometry confirm the retention of dissymmetry in both solution and solid states. The dissymmetric complexes all show greater photoluminescence (PL) quantum yields (ϕPL) than the corresponding symmetric complexes, allowing red to near-infrared emissions with large pseudo-Stokes shifts. The best performance achieves a maximum PL wavelength of 671 nm, a pseudo-Stokes shift of 5400 cm–1, and ϕPL of 0.62–0.72 in toluene (dielectric constant εs = 2.4), dichloromethane (εs = 9.1), acetone (εs = 21.4), and ethanol (εs = 24.3). The large pseudo-Stokes shift is distinctive considering BODIPYs with small Stokes shifts (∼500 cm–1), and the ϕPL values are higher than or comparable to those of BODIPYs fluorescing at similar wavelengths. Electrochemistry and density functional theory calculations illustrate that frontier orbital ordering in the dissymmetric complexes meets the condition for efficient PL proposed in our theory.

This Communication reports the first observation of solid-state photoluminescence in bis(dipyrrinato)zinc(II) complexes with various substituents. The report discusses the effect of their substituents on their crystal structures and spectroscopic properties. Their meso-aryl groups are revealed to play important roles in the spectroscopic properties in the solid state.

Bottom-up approaches have gained significant attention recently for the creation of nano-sized, ordered functional structures and materials. Stepwise coordination techniques, in which ligand molecules and metal sources are reacted alternatively, offer several advantages. Coordination bonds are stable, reversible, and self-assembling, and the resultant metal complex motifs may contain functionalities unique to their own characteristics. This review focuses on metal complex wire systems, specifically the bottom-up fabrication of linear and branched bis(terpyridine)metal complex wires on electrode surfaces. This system possesses distinct and characteristic electronic functionalities, intra-wire redox conduction and excellent long-range electron transport ability. This series of comprehensive studies exploited the customizability of bis(terpyridine)metal complex wires, including examining the influence of building blocks. In addition, simple yet effective electron transfer models were established for redox conduction and long-range electron transport. A fabrication technique for an ultra-long bis(terpyridine)metal complex wire is also described, along with its properties and functionalities.

One-dimensional coordination polymers (1D-CPs) tend either to dissociate into constitutive ligands and metals readily in solution, or to aggregate randomly and amorphously, which prevents them from widespread application. In the present research, 1D-CPs comprising bridging dipyrrin ligands and divalent metal ions (Zn2+, Ni2+, and Cu2+) are synthesized. A liquid/liquid interfacial reaction gives rise to single crystals suitable for X-ray diffraction analysis: A dichloromethane solution of the ligand is layered with aqueous metal(II) acetate, such that the coordination reaction proceeds at the liquid/liquid interface. Isolated single fibers of the zinc coordination polymer may be exfoliated from the single crystal or bulk solid upon ultrasonication. Atomic force microscopy (AFM) detects the isolated fibers with lengths of more than several μm. The exfoliated 1D-CP wires feature good processability, realizing a conjugate with single-wall carbon nanotubes (SWCNTs), and a thin film on a transparent SnO2 electrode. The processed materials show electric conversion ability: For example, the modified SnO2 electrode serves as a photoanode for a photoelectric conversion system. The designability and tunability of the present 1D-CPs is demonstrated by a ligand modification, affording a luminescent property and an extension of the photoelectric conversion response to longer wavelengths.

Dipyrrins serve as monovalent bidentate ligand molecules that coordinate to various cations. Their BF2 complexes, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its derivatives (BODIPYs), exhibit excellent photostability, strong light absorption, and high fluorescence quantum yield, thereby encouraging their application in various fields, e.g., as biological and biomedical fluorescent markers. Dipyrrin may also accept a wide variety of metal ions spontaneously. However, dipyrrin metal complexes have been disregarded from materials science research. This review article summarizes recent progress in bis(dipyrrinato)metal(II) and tris(dipyrrinato)metal(III) complexes from the viewpoint of materials chemistry. Section 2 describes a series of efforts aimed to realize intense luminescence superior to or comparable with that of BODIPYs. The spontaneous coordination of these complexes enables them to construct self-assembled nanoarchitectures, such as supramolecules and coordination polymers that form one-dimensional nanowires, two-dimensional nanosheets, and metal–organic frameworks. Section 3 describes such alluring molecular superstructures. Section 4 discusses potential applications based on these nanoarchitectures, such as thermoelectric and photoelectric conversion.

Heteroleptic bis(dipyrrinato)copper(II) and nickel(II) complexes are synthesized. Their structures are determined by X-ray diffraction analysis, and their properties are investigated by using cyclic voltammetry, chronocoulometry, and UV/vis absorption spectroscopy.

The authors reported previously that bis(terpyiridne)iron(II) complex oligomer wires possess outstanding long-range intrawire electron transport ability. Here, molecular arrays of gold-electrode–bis(terpyridine)iron(II)–ferrocene are constructed by stepwise coordination as simple models of the oligomer wire system. The fast electron transfer between the terminal ferrocene and the gold electrode through the bis(terpyiridne)iron(II) complex unit is studied by potential step chronoamperometry (PSCA) and electrochemical impedance spectroscopy (EIS). Tafel plots derived from PSCA are analyzed based on Marcus theory. The plots reveal greater first-order electron transfer rate constant, weaker electronic coupling between the terminal ferrocene and the gold electrode, and smaller reorganization energy than shown by a conventional ferrocenylalkanethiol self-assembled monolayer. The electron transfer rate constants estimated by EIS agree with the PSCA results.

Asymmetric, heteroleptic dinuclear bis(dipyrrinato)zinc(II) complexes were synthesized and demonstrated to collect a wide range of light across the UV and visible regions (340–655 nm). The complexes also conveyed excitons across their structure from one end to the other, with spectroscopic studies demonstrating quantitative and fast energy transfer.

To provide an improvement over the low fluorescence efficiencies often shown by homoleptic tris(dipyrrinato)indium(III) complexes, luminescent heteroleptic tris(dipyrrinato)indium(III) complexes bearing two types of dipyrrinato ligands are designed here by theoretical calculation and then synthesized. They possess frontier orbitals linked to suppression of the nonemissive charge-separated states; one shows a high fluorescence quantum yield (0.41) in toluene, which exceeds that of the corresponding BF2 complex.

Previously, we synthesized π-conjugated trinuclear metalladithiolene complexes based on benzenehexathiol (J. Chem. Soc., Dalton Trans.1998, 2651; Dalton Trans.2009, 1939; Inorg. Chem.2011, 50, 6856). Here we report trinuclear complexes with a triphenylene backbone. A reaction with triphenylenehexathiol and group 9 metal precursors in the presence of triethylamine gives rise to trinuclear complexes 9–11. The planar structure of 11 is determined using single crystal X-ray diffraction analysis. The ligand-to-metal charge transfer bands of 9–11 move to longer wavelengths compared with those of mononuclear 12–14. Electrochemical measurements disclose that the one-electron and two-electron reduced mixed-valent states are stabilized thermodynamically. UV–vis–NIR spectroscopy for the reduced species of 9 identifies intervalence charge transfer bands for 9– and 92–, substantiating the existence of electronic communication among the three metal nuclei. These observations prove that the triphenylene backbone transmits π-conjugation among the three metalladithiolene units.

We synthesised heteroleptic azadipyrrinato–dipyrrinato hybrid zinc(II) complex 1-Zn-2, by means of the stepwise coordination method. Homoleptic bis(azadipyrrinato)zinc(II) complex 1-Zn-1 was non-fluorescent, whereas 1-Zn-2 exhibited detectable fluorescence from azadipyrrinato ligand 1.

This Perspective addresses our recent studies relating to metalladithiolenes and their cluster complexes that exhibit peculiar electronic communication in mixed-valent (MV) states. Chapter 1 provides an introduction for the Perspective. Chapter 2 enumerates a series of phenylene-annulated π-conjugated trinuclear metalladithiolenes with intense electronic communication in the MV states. Chapter 3 treats heterometal cluster complexes synthesized by integrating zero-valent metal carbonyls on mononuclear metalladithiolenes, taking advantage of the coordination unsaturation of the latter. In the field of MV chemistry, their electronic communication through metal–metal bonds and potential inversion behavior are intriguing properties. Chapter 4 describes hexanuclear and nonanuclear heterometal cluster complexes created in combination with the methods introduced in Chapters 2 and 3. The resultant heterometal cluster complexes feature electronic communication through the vast phenylene-annulated π-conjugated trinuclear metalladithiolene frameworks, the intensity of which correlates with their planarity. Each chapter describes the synthesis, structural features, and electrochemical properties of the relevant compounds.

Slipped cofacial porphyrin dimer 12 with di-p-anisylamino groups on the meso-positions shows characteristic photo- and electroproperties making it suitable as a photosynthetic special pair model: more intense and red-shifted absorptivities in the visible region, and electronic communication between the two porphyrins in mixed-valent cation radical 12+, which is quantified with an IVCT band analysis.

We synthesised heteroleptic azadipyrrinato–dipyrrinato hybrid zinc(II) complex 1-Zn-2, by means of the stepwise coordination method. Homoleptic bis(azadipyrrinato)zinc(II) complex 1-Zn-1 was non-fluorescent, whereas 1-Zn-2 exhibited detectable fluorescence from azadipyrrinato ligand 1.

One-dimensional coordination polymers (1D-CPs) tend either to dissociate into constitutive ligands and metals readily in solution, or to aggregate randomly and amorphously, which prevents them from widespread application. In the present research, 1D-CPs comprising bridging dipyrrin ligands and divalent metal ions (Zn2+, Ni2+, and Cu2+) are synthesized. A liquid/liquid interfacial reaction gives rise to single crystals suitable for X-ray diffraction analysis: A dichloromethane solution of the ligand is layered with aqueous metal(II) acetate, such that the coordination reaction proceeds at the liquid/liquid interface. Isolated single fibers of the zinc coordination polymer may be exfoliated from the single crystal or bulk solid upon ultrasonication. Atomic force microscopy (AFM) detects the isolated fibers with lengths of more than several μm. The exfoliated 1D-CP wires feature good processability, realizing a conjugate with single-wall carbon nanotubes (SWCNTs), and a thin film on a transparent SnO2 electrode. The processed materials show electric conversion ability: For example, the modified SnO2 electrode serves as a photoanode for a photoelectric conversion system. The designability and tunability of the present 1D-CPs is demonstrated by a ligand modification, affording a luminescent property and an extension of the photoelectric conversion response to longer wavelengths.

The authors create a zinc(II) complex featuring a simple chemical structure but multi-functional luminochromism. Reversible dissociation/association between the zinc center and the terpyridine ligand plays a key role in the multi-functional luminochromism.

Imine-linked BODIPY oligomers show fluorescence quantum yields of up to 0.93. The azine linker may mediate π-conjugation that extends over six BODIPY units with redshifts up to 125 nm. BODIPYs are immobilized on silica gel through heterogeneous imine-bond formation, being fluorescent and robust.

Asymmetric, heteroleptic dinuclear bis(dipyrrinato)zinc(II) complexes were synthesized and demonstrated to collect a wide range of light across the UV and visible regions (340–655 nm). The complexes also conveyed excitons across their structure from one end to the other, with spectroscopic studies demonstrating quantitative and fast energy transfer.

Slipped cofacial porphyrin dimer 12 with di-p-anisylamino groups on the meso-positions shows characteristic photo- and electroproperties making it suitable as a photosynthetic special pair model: more intense and red-shifted absorptivities in the visible region, and electronic communication between the two porphyrins in mixed-valent cation radical 12+, which is quantified with an IVCT band analysis.

Bottom-up approaches have gained significant attention recently for the creation of nano-sized, ordered functional structures and materials. Stepwise coordination techniques, in which ligand molecules and metal sources are reacted alternatively, offer several advantages. Coordination bonds are stable, reversible, and self-assembling, and the resultant metal complex motifs may contain functionalities unique to their own characteristics. This review focuses on metal complex wire systems, specifically the bottom-up fabrication of linear and branched bis(terpyridine)metal complex wires on electrode surfaces. This system possesses distinct and characteristic electronic functionalities, intra-wire redox conduction and excellent long-range electron transport ability. This series of comprehensive studies exploited the customizability of bis(terpyridine)metal complex wires, including examining the influence of building blocks. In addition, simple yet effective electron transfer models were established for redox conduction and long-range electron transport. A fabrication technique for an ultra-long bis(terpyridine)metal complex wire is also described, along with its properties and functionalities.

Heteroleptic bis(dipyrrinato)copper(II) and nickel(II) complexes are synthesized. Their structures are determined by X-ray diffraction analysis, and their properties are investigated by using cyclic voltammetry, chronocoulometry, and UV/vis absorption spectroscopy.

This Perspective addresses our recent studies relating to metalladithiolenes and their cluster complexes that exhibit peculiar electronic communication in mixed-valent (MV) states. Chapter 1 provides an introduction for the Perspective. Chapter 2 enumerates a series of phenylene-annulated π-conjugated trinuclear metalladithiolenes with intense electronic communication in the MV states. Chapter 3 treats heterometal cluster complexes synthesized by integrating zero-valent metal carbonyls on mononuclear metalladithiolenes, taking advantage of the coordination unsaturation of the latter. In the field of MV chemistry, their electronic communication through metal–metal bonds and potential inversion behavior are intriguing properties. Chapter 4 describes hexanuclear and nonanuclear heterometal cluster complexes created in combination with the methods introduced in Chapters 2 and 3. The resultant heterometal cluster complexes feature electronic communication through the vast phenylene-annulated π-conjugated trinuclear metalladithiolene frameworks, the intensity of which correlates with their planarity. Each chapter describes the synthesis, structural features, and electrochemical properties of the relevant compounds.

Dipyrrins serve as monovalent bidentate ligand molecules that coordinate to various cations. Their BF2 complexes, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its derivatives (BODIPYs), exhibit excellent photostability, strong light absorption, and high fluorescence quantum yield, thereby encouraging their application in various fields, e.g., as biological and biomedical fluorescent markers. Dipyrrin may also accept a wide variety of metal ions spontaneously. However, dipyrrin metal complexes have been disregarded from materials science research. This review article summarizes recent progress in bis(dipyrrinato)metal(II) and tris(dipyrrinato)metal(III) complexes from the viewpoint of materials chemistry. Section 2 describes a series of efforts aimed to realize intense luminescence superior to or comparable with that of BODIPYs. The spontaneous coordination of these complexes enables them to construct self-assembled nanoarchitectures, such as supramolecules and coordination polymers that form one-dimensional nanowires, two-dimensional nanosheets, and metal–organic frameworks. Section 3 describes such alluring molecular superstructures. Section 4 discusses potential applications based on these nanoarchitectures, such as thermoelectric and photoelectric conversion.