Porphyrin-Sensitizers and Anthracene-Annihilators Built in Isostructural Frameworks for Investigating Triplet-Triplet Annihilation Upconversion.

In this study, four isostructural pillar-layered frameworks were constructed using a porphyrin layer and an anthracene pillar, which served as the sensitizer and annihilator, respectively, in the triplet-triplet annihilation upconversion (TTA-UC) system. Framework demonstrated the highest upconversion quantum yield of 1.01%.

Polypyridyl Ru(II) or cyclometalated Ir(III) functionalized architectures for photocatalysis.

The chemistry of polypyridyl Ru(II) and cyclometalated Ir(III) derivatives provides long-lasting interest to researchers due to the inherent advantage of their triplet states in a variety of photoactivities. The introduction of Ru(N^N) and Ir(C^N)(X^N) modules into well-defined architectures extends the research areas of both photoactive metal complexes and network chemistry, generating a lot of new opportunities with interesting structural aesthetics and profound functional possibilities. The rapid development of research in integrating Ru(II) or Ir(III) metallotecons into the architectures has been apparent in recent years which makes this a fascinating subject for reviewing.

Photoreactive Crystals Exhibiting [2 + 2] Photocycloaddition Reaction and Dynamic Effects.

ConspectusConducting a reaction in the solid state eliminates the usage of solvents. If such reactions are conducted in a single-crystal to single-crystal (SCSC) fashion, then structural characterization by single-crystal X-ray crystallography (SCXRD) techniques provides unequivocal structural details. Although topochemical principles govern, getting single crystals at the end of a SCSC reaction purely depends on the experimental skills of the researchers.

Highly Efficient Multiphoton Absorption of Zinc-AIEgen Metal-Organic Frameworks.

A series of luminescent frameworks was synthesized from the selective combination of aggregation induced emission (AIE)-linker tetra-(4-carboxylphenyl)ethylene (H TCPE) and Zn . Complex 1 was formed by the close packing of Zn-TCPE hinge, and isostructural complexes 2-5 were constructed by the linkage of Zn-TCPE layer and pillar ligands. These complexes exhibit highly efficient multiphoton excited photoluminescence (MEPL) and concomitant third-harmonic generation (THG).

Impact of the Structural Modification of Diamondoid Cd(II) MOFs on the Nonlinear Optical Properties.

A change in the degree of interpenetration (DOI) in metal-organic frameworks (MOFs) prompted by heat, pressure, or exchange of solvents is a fascinating phenomenon that can potentially impact the functional properties of MOFs. Structural transformation involving two noncentrosymmetric MOFs with different DOIs provides a rare opportunity to manipulate their optical properties. Herein, we report an unusual single-crystal-to-single-crystal (SCSC) transformation of a noncentrosymmetric 7-fold interpenetrated diamondoid () Cd(II) MOF into another noncentrosymmetric but 8-fold interpenetrated MOF upon the removal of guest solvents.

Anisotropic Two-Photon Absorption and Second Harmonic Generation in Single Crystals of Silver(I) Coordination Complexes.

Metal complexes have been gaining attention in recent times over the traditional inorganic materials such as nonlinear optical materials. Here, we report both two-photon absorption (2PA) and second harmonic generation (SHG) from single crystals of two Ag(I) complexes with considerable optical anisotropy. We demonstrate that by controlling the incident light polarization, the tunability between these two nonlinear optical processes can be achieved.

Construction of 2D Interdigitated Polyrotaxane Layers and their Transformation to a 3D Polyrotaxane by a Photocycloaddition Reaction between Wheels.

Following the pioneering work of Sauvage and Stoddart on rotaxanes, construction of higher dimensional polyrotaxanes in metal-organic frameworks (MOFs) via a modified protocol is challenging. We present the formation of a two-dimensional (2D) polyrotaxane and its conversion to a three-dimensional (3D) polyrotaxane MOF via a photoreaction between interdigitated "olefin wheels". For this purpose, a 2-fold entangled 2D MOF [Pb(bpp)(sdc)] (), showing a 2D + 2D → 2D polyrotaxane motif, has been synthesized from the solvothermal reaction of lead(II) nitrate, 3,3'-stilbenedicarboxylic acid (Hsdc) containing an olefin group, and 1,4-bis(4-pyridyl)piperazine (bpp).

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications.

Among the recent developments in metal-organic frameworks (MOFs), porous layered coordination polymers (CPs) have garnered attention due to their modular nature and tunable structures. These factors enable a number of properties and applications, including gas and guest sorption, storage and separation of gases and small molecules, catalysis, luminescence, sensing, magnetism, and energy storage and conversion. Among MOFs, two-dimensional (2D) compounds are also known as 2D CPs or 2D MOFs.

Reversible Thermosalience in a One-Dimensional Coordination Polymer Preceded by Anisotropic Thermal Expansion and the Shape Memory Effect.

Thermally responsive crystals hold great potential for their use as actuating materials by acting as energy transducers to convert heat energy to mechanical work. Control over defined phase transition temperature with rapid reconfiguration is of great advantage for actuation. The thermosalient (TS) effect is a rarely observed phenomenon in coordination polymers (CPs), let alone the reversibility of thermosalience in CPs.

Single-Crystal-to-Single-Crystal [2 + 2] Photocycloaddition Reaction in a Photosalient One-Dimensional Coordination Polymer of Pb(II).

In a remarkable example, we report a one-dimensional coordination polymer (CP) of Pb(II) showing photosalient (PS) properties triggered by [2 + 2] cycloaddition of olefinic ligands, which is seldom observed in CPs. Macroscopic rod-shaped crystals show various photomechanical effects such as jumping, splitting, rolling, and breaking upon UV illumination. In this rare example, we could determine the solid-state structure of the 100% dimerized product and three intermediate structures, even after the shattering of crystals into small pieces.

Water Stable Zn(II) Metal-Organic Framework as a Selective and Sensitive Luminescent Probe for Fe(III) and Chromate Ions.

Sensing and monitoring toxic contaminants like Fe, CrO, and CrO ions in water is very important due to their harmful effects on biological and environmental systems. Enhanced hydrolytic stability, sensitivity, and selectivity, in addition to their excellent luminescence properties, are important attributes of metal-organic framework (MOF)-based sensors for sensing applications. In this work, the water stable Zn-MOF [Zn(tpeb)(bpdc)] (where tpeb = 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and bpdc = biphenyl-4,4'-dicarboxylic acid) was synthesized and characterized.

Rotation of a helical coordination polymer by mechanical grinding.

Anisotropic cell volume expansion by mechanical grinding of the solid facilitates the concerted rotation of the photo-inert helical coordination polymer, which causes the misaligned arms containing olefin functional groups in the neighbouring strands to align to undergo [2+2] cycloaddition reaction in 83% yield.

Disappeared supramolecular isomer reappears with perylene guest.

Among different types of polymorphism, disappearing polymorphism deals with the metastable kinetic form which can not be reproduced after its first isolation. In the world of coordination polymers (CPs) and metal-organic frameworks (MOFs), despite the fact that many types of supramolecular isomerism exist, we are unaware of disappearing supramolecular isomerism akin to disappearing polymorphism. This work reports a MOF with topology that could not be reproduced, but subsequent synthesis yielded another supramolecular isomer, a double-pillared-layer MOF.

Extraordinary anisotropic thermal expansion in photosalient crystals.

Although a plethora of metal complexes have been characterized, those having multifunctional properties are very rare. This article reports three isotypical complexes, namely [Cu(benzoate) ], where = 4-styryl-pyridine (4spy) (), 2'-fluoro-4-styryl-pyridine (2F-4spy) () and 3'-fluoro-4-styryl-pyridine (3F-4spy) (), which show photosalient behavior (photoinduced crystal mobility) while they undergo [2+2] cyclo-addition. These crystals also exhibit anisotropic thermal expansion when heated from room temperature to 200°C.

Straight, bendable and bent organic crystals.

trans-4-Phenylazobenzoic acid (pab) crystallized in three different morphologies: long rod-like crystals, bendable long thin crystals, and bent crystals. Of them, the bent crystals were obtained by recrystallizing after subjecting pab to UV-irradiation in solution. A small amount of cis-form in the bent crystals is responsible for the bent nature, while the elastic bending of thin platy crystals can be understood from the crystal packing.

Giant Enhancement of Second Harmonic Generation Accompanied by the Structural Transformation of 7-Fold to 8-Fold Interpenetrated Metal-Organic Frameworks (MOFs).

Interpenetration in metal-organic frameworks (MOFs) is an intriguing phenomenon with significant impacts on their properties, and functional applications. Herein, we show that a 7-fold interpenetrated MOF (1) is transformed into an 8-fold interpenetrated MOF by the loss of DMF in a single-crystal-to-single-crystal manner. This is accompanied by a giant enhancement of the second harmonic generation (SHG ca.

Chemical Patterning in Single Crystals of Metal-Organic Frameworks by [2+2] Cycloaddition Reaction.

Conventional chemical patterning involves films of polymeric materials. Herein, we demonstrate that the presence or absence of guest solvents in the crystal voids modulates the patterning of the cyclobutane rings in highly strained metal-organic frameworks (MOFs) under UV light. The olefin pairs of the spacer ligands, which resemble a ladder-like structure, in the MOF, undergo a [2+2] cycloaddition reaction in a single-crystal-to-single-crystal manner.

Solid-State Photochemical [2+2] Cycloaddition Reaction of Mn Complexes.

Three Mn complexes have been synthesized under similar experimental conditions. Of these [Mn (benzoate) (L) ] (where L=4-styrylpyridine or 4spy, 1 and 2-fluoro-4'-styrylpyridine or 2F-4spy, 3) are paddlewheel complexes, but crystallized in different space groups. Whereas [Mn (benzoate) (3F-4spy) ] (3F-4spy=3-fluoro-4'-styrylpyridine), 4 is a dinuclear complex having different stoichiometry from 1 and 3 with two pairs of 3F-4spy ligands aligned in face-to-face manner.

Near-White Light Emission from Lead(II) Metal-Organic Frameworks.

Reaction of bpy (bpy = 4,4'-bipyridine) with Pb(OAc)·3HO in DMF (DMF = dimethylformamide) afforded a metal-organic framework (MOF), [Pb(μ-bpy)(μ-OCCH)(μ-OCCH)]·HO (1). Reaction of bpy with Pb(OCCF) in a methanol and chloroform mixture furnished another MOF, [Pb(μ-bpy)(μ-OCCF)]·/CHCl (2). However, the reaction of bpy with Pb(OAc)·3HO in the presence of trifluoroacetic acid in a similar reaction condition yielded a hydrogen-bonded zwitter-ionic complex of Pb(II), [Pb(bpy-H)(OCCF)] (3).

Isomerism in double-pillared-layer coordination polymers - structures and photoreactivity.

The existence of isomerism in coordination polymeric structures offers opportunities to understand structure-function relationships. Herein the serendipitous isolation is reported of two isomeric double-pillared-layer coordination polymeric structures arising from two different types of carboxyl-ate bonding of benzene-1,4-di-carboxyl-ate ligands to zinc(II), which constitutes a new type of structural isomerism. The different bonding modes not only alter the shape and size of the pores, but also the nature of interpenetration and photoreactivity.

The role of structure and the metal ion in the fluorescence sensing of nitro compounds for a series of lanthanide(iii) 9,10-anthracene dicarboxylate coordination polymers.

Twenty-eight lanthanide coordination polymers (CPs) containing 9,10-anthracene dicarboxylate (ADC) linkers have been synthesized and characterized. For the earlier class of lanthanides La, Ce, Pr, Nd, Sm, Eu, Gd and Tb, the 3D pcu net was generated from dimethylformamide (DMF) while a 2D hcb net was formed using dimethylacetamide (DMA). Similarly for the later class of lanthanides, Dy, Ho, Er, Tm, Yb and Lu, a 2D hcb net was formed when dimethylacetamide (DMA) was used.

Photochemical reactions of metal complexes in the solid state.

This perspective focusses on the solid-state reactivity and structural transformation driven by photochemical methods in discrete metal complexes, organometallic compounds, metallo-macrocycles and cages. Changes in the metal-metal bond distances, racemization of chiral centres, fusion of cages, formation of coordination polymers, expected [2 + 2] and [4 + 4] cycloaddition products, unusual phenyl-olefin dimerization, and linkage isomerization of -SO, -NO & -NO ligands cause the structural transformations. Of these, [2 + 2] photo-cycloaddition reactions have been widely studied and the photoreactions are made possible by various supramolecular interactions including hydrogen bonds, metallophilic, ππ and C-Hπ interactions, ligand design and metallic clips to bring the reactive functional groups closely into correct orientation close to the transition state.

Regulating thermosalient behaviour in three polymorphs.

Three polymorphs of a di-chloro--salicylideneaniline derivative show visually impressive jumping and sudden blasting behaviours on heating due to phase transitions.

Curved crystal morphology, photoreactivity and photosalient behaviour of mononuclear Zn(II) complexes.

A dramatic effect of crystal morphology, photoreactivity and photosalient property is observed in a zinc(II) complex due to solvent effects and fluorine substitution at the backbone of the ligand. Of the two crystal forms with a 3-fluoro derivative, one yielded a curved morphology of single crystals and the second form shows photoreactivity in the solid state, whereas crystals of the 2-fluoro derivative pop during the [2 + 2] photocycloaddition reaction. This is the first report documenting curved single crystals of metal complexes obtained naturally during crystallization, although such bent crystals have been observed in extended solids naturally, or bent by mechanical force or by UV irradiation.