Sequential Assembly and Stabilization of Cu6S6 Octahedral Clusters in NaCl-, NiAs-, and CdI2-Related Structures and Their Utility toward Thermochromism and Multicomponent Hantzsch Reaction

Seven new inorganic-organic coordination polymer compounds have been synthesized and their structures are determined by single-crystal structure determination. The compounds were prepared by the sequential assembly of a [Cu₆(mna)₆]^6- moiety in the presence of a Mn salt and a secondary amine ligand. Of the seven compounds, [{Cu₆(mna)₆}Mn₃(H₂O)(H₂O)_1.5]·5.5H₂O (I), [{Cu₆(mna)₆}Mn₃(H₂O)(Im)_1.5]·3.5H₂O (Ia), [{Cu₆(mna)₆}{Mn(BPY)(H₂O)}₂{Mn(H₂O)₄}]·2H₂O (III), and [{Cu₆(mna)₆}{Mn(BPE)_0.5(H₂O)₂}₂{Mn(BPE)(H₂O)₂}] (IV) have a three-dimensional structure, whereas [{Cu₆(mna)_4.5(Hmna)_1.5}{Mn(BPA)(H₂O)₂}{Mn(H₂O)}]{Mn_0.25(H₂O)₃}·7H₂O (II), [{Cu₆(mna)₆}{Mn(4-BPDB)_0.5H₂O}{Mn(H₂O)₂}].{Mn(H₂O)₆}·6H₂O (V), and [{Cu₆(mna)₄(Hmna)₂}·{Mn(H₂O)₃}₂]·(4-APY)₂·6H₂O (VI) have a two-dimensional structure. Some of the prepared compounds exhibit structures that closely resemble the classical inorganic structures, such as NaCl (Ia, III), NiAs (I), and CdI₂ (IV and VI). The stabilization of such simple structures from the assembly of octahedral Cu₆S₆ clusters and different Mn species and aromatic nitrogen-containing ligands suggests the subtle interplay between the constituent reactants. The compounds were examined for the multicomponent Hantzsch reaction, which gave the product in good yields. The compounds, II and VI, on heating to 70 °C change color reversibly from pale yellow to deep red, which suggests the possible use of these compounds as thermochromic materials. The present study suggests that the Cu₆S₆ octahedral clusters can be assembled into structures that resemble classical inorganic structures.

Vapochromic crystals: understanding vapochromism from the perspective of crystal engineering

Vapochromic materials, which undergo colour and/or emission changes upon exposure to certain vapours or gases, have received increasing attention recently because of their wide range of applications in, e.g., chemical sensors, light-emitting diodes, and environmental monitors. Vapochromic crystals, as a specific kind of vapochromic materials, can be investigated from the perspective of crystal engineering to understand the mechanism of vapochromism. Moreover, understanding the vapochromism mechanism will be beneficial to design and prepare task-specific vapochromic crystals as one kind of low-cost 'electronic nose' to detect toxic gases or volatile organic compounds. This review provides important information in a broad scientific context to develop new vapochromic materials, which covers organometallic or coordination complexes and organic crystals, as well as the different mechanisms of the related vapochromic behaviour. In addition, recent examples of supramolecular vapochromic crystals and metal-organic-framework (MOFs) vapochromic crystals are introduced.

Pyridylphosphine supported Ag(i) and Cu(i) complexes for detection of alcohols and nitriles via structural transformations from 1D to 0D

One-dimensional chain Ag(i) and Cu(i) complexes exhibit vapochromic luminescence for the detection of alcohols and nitriles via structural transformations from 1D to 0D.

Two-way vapochromism of a luminescent platinum(ii) complex with phosphonic-acid-functionalized bipyridine ligand

A luminescent Pt(ii) complex bearing a phosphonic-acid-functionalized bipyridine ligand was successfully synthesized and its unique two-way vapochromic behaviour investigated.

A metalloligand appended with benzimidazole rings: tetranuclear [CoZn3] and [CoCd3] complexes and their catalytic applications

A novel Co³⁺-based metalloligand, offering appended benzimidazole rings, has been utilized for the synthesis of catalytically active tetranuclear [CoZn₃] and [CoCd₃] heterometallic coordination complexes.

Development of Ion-Conductive and Vapoluminescent Porous Coordination Polymers Composed of Ruthenium(II) Metalloligand

We synthesized two new porous coordination polymers (PCPs) {Ln₇(OH)₅[Ru(dcbpy)₃]₄·4nH₂O} (Ln₇-Ru₄; Ln = Ce, Nd) composed of the luminescent ruthenium(II) metalloligand [Ru(4,4'-dcbpy)₃]^4- ([4Ru]; 4,4'-dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and lanthanide ions Ln³⁺ (Ln = Ce, Nd). These two PCPs Ln₇-Ru₄ are isomorphous with the previously reported PCP La₇-Ru₄, and the lattice constants (a, c, and unit cell volume V) changed systematically according to the lanthanide contraction. All three Ln₇-Ru₄ compounds have OH^- anion containing porous structures and a large number of hydrate water molecules within the pores, resulting in moderate ion conductivities (10^-6-10^-7 S cm^-1) at 90% relative humidity (RH) and 298 K. In contrast, the structural transformation of Ln₇-Ru₄ associated with water-vapor adsorption/desorption strongly depends on the lanthanide ion; the Ln₇-Ru₄ compounds with larger Ln³⁺ ions recover the original porous structure at lower relative humidities (RH). A similar trend was observed for the ion conduction activation energy, suggesting that the bridging Ln³⁺ ion plays an important role in the formation of the ion-conductive pathways. La₇-Ru₄ and Ce₇-Ru₄ exhibit vapochromic luminescence associated with water vapor adsorption/desorption, arising from the ³MLCT emission of [4Ru]. This vapochromic behavior is also affected by the replacement of the Ln³⁺ ion; the vapochromic shift of Ce₇-Ru₄ was observed at RH values (near 100% RH) higher than that of La₇-Ru₄. ³MLCT emissions of the [4Ru] metalloligand in Nd₇-Ru₄ were barely observable in the visible region, but sharp emission bands characteristic of 4f-4f transitions of the Nd³⁺ ion were observed in the near-infrared (NIR) region (arising from the ¹MLCT transition of [4Ru]), suggesting the transfer of energy from the [4Ru] ³MLCT excited state to the 4f-4f transition state of the Nd³⁺ ions.

Unravelling chromism in metal–organic frameworks

Chromophoric MOFs are reviewed, focussing on those which change colour on application of external stimuli such as heat, pressure, light or chemical environment.

Luminescence of tartrate bridged dinuclear 2,2′-bipyridine platinum(ii) complexes: emission color controlled by intra- and inter-molecular interactions in the solid state

Mono- and dinuclear Pt^II complexes with tartrate (tartH₂²⁻) [Pt(bpy)(tartH₂)] and [{Pt(bpy)}₂(μ-tart)], respectively, in crystals exhibited an emission color controlled by intra- and inter-molecular Pt–Pt and/or π–π interactions.

A Highly Water-Tolerant Magnesium(II) Coordination Polymer Derived from a Flexible Layered Structure

A two-dimensional (2D) layered Mg(II) coordination polymer (CP) with a high tolerance for H2 O was designed, synthesised, and crystallographically characterised. The synthesis was achieved by the introduction of a flexible 2D layered structure composed of Mg(II) ions and isonicotinate N-oxide ligands. Owing to its high H2 O tolerance, the obtained 2D layered structure has the flexibility to repeatedly adsorb a large amount of H2 O associated with interlayer expansion and enable the removal of H2 O from a H2 O/2-propanol mixed vapour. These results indicate that the CP could be an excellent dehydrating agent.

Proton-switchable vapochromic behaviour of a platinum(ii)–carboxy-terpyridine complex

We synthesized a carboxy-functionalized Pt(ii)–terpyridine complex that exhibits vapochromic behavior that is switchable via protonation/deprotonation of the carboxy group.

Recent advances in metal–organic frameworks based on pyridylbenzoate ligands: properties and applications

In this mini-review we discuss the properties and applications of metal–organic frameworks based on pyridylbenzoate.

Supramolecular assembly of metal-ligand chromophores for sensing and phosphorescent OLED applications

The exploration of phosphorescent materials based on transition metal-ligand chromophoric complexes represents an important area of research in molecular materials. The knowledge and fundamental understanding of their photophysical properties offer a possible fine-tuning of their electronic absorption and luminescence properties. The strong propensity of d(8) transition metal compounds to form non-covalent metal···metal interactions facilitates supramolecular assembly and the formation of supramolecular nanostructures with interesting photophysical properties. The introduction of supramolecular assembly with hierarchical complexity involving non-covalent interactions could lead to research dimensions of unlimited possibilities and opportunities. This article briefly summarizes the latest progress on the use of d(8) metal-ligand chromophores as chemosensors, as exemplified by alkynylplatinum(II) complexes with emphasis on supramolecular assembly involving non-covalent interactions, and the recent advances in the utilization of d(8) metal-ligand phosphors, as exemplified by alkynylgold(III) system, for the exploration and development of phosphorescent OLEDs.

Thermo- and mechanical-grinding-triggered color and luminescence switches of the diimine-platinum(II) complex with 4-bromo-2,2'-bipyridine

The square-planar diimine-platinum(II) complex, Pt(4-Brbpy)(C≡CC6H5)2 (1) (4-Brbpy = 4-bromo-2,2'-bipyridine), was prepared and characterized. Solid-state 1 exhibits reversible thermo- and mechanical-grinding-triggered color and luminescence changes. When crystalline 1·2(CH2Cl2) or 1·2(CHCl3) are heated or ground, the original bright yellow-green emission centered at 525 (549, sh) nm changed to 637 and 690 nm, corresponding to thermo- and mechanochromic response shifts of approximately 88-112 nm and 141-165 nm, respectively. Meanwhile the crystalline state changes into an amorphous phase in both processes. Once the amorphous sample absorbs organic vapors, it can be reverted to the original crystalline state, along with red luminescence turning back to yellow-green emission. The reversibility of thermo- and mechanical-grinding-triggered chromic luminescence properties has been dynamically monitored by emission spectra and X-ray diffraction patterns. The dramatic thermo- and mechanical-grinding-triggered emission red shifts are most likely due to the conversion of the (3)MLCT/(3)LLCT emission state into the (3)MMLCT triplet state.

A new class of highly solvatochromic dicyano rhenate(I) diimine complexes--synthesis, photophysics and photocatalysis

A new class of dicarbonyl dicyano rhenate(I) diimine complexes, cis,trans-[Re(CO)(2)(CN)(2)(N-N)](-), with highly environmentally sensitive MLCT absorption and emission properties was synthesised and characterised. Preliminary experiments revealed that these complexes are active photocatalysts for CO(2) reduction.