Icosidodecahedral Coordination-Saturated Cuprofullerene.

The first coordination-saturated buckyball with a C60 molecule totally encased in an icosidodecahedral Cu30 in a (µ30 -(η2 )30 )-fashion, namely C60 @Cu30 @Cl36 N12 , has been successfully realized by a C60 -templated assembly. The 48 outmost coordinating atoms (36Cl+12N) comprise a new simple polyhedron that is described by a ccf topology. Charge transfer from (CuI , Cl) to C60 explains the expansion of the light absorption up to 700 nm, and accounts for an ultrafast photophysical process that underpins its high photothermal conversion efficiency. This work makes a giant step forward in exohedral metallofullerene (ExMF) chemistry.

Symmetry-Driven Assembly of a Penta-Shell Keplerate Cuprofullerene for Metallofullerene Frameworks.

Two metallofullerene frameworks (MFFs) constructed from a penta-shell Keplerate cuprofullerene chloride, C60 @Cu24 @Cl44 @Cu12 @Cl12 , have been successfully prepared via a C60 -templated symmetry-driven strategy. The icosahedral cuprofullerene chloride is assembled on a C60 molecule through [η2 -(C=C)]-CuI and CuI -Cl coordination bonds, resulting in the penta-shell Keplerate with the C60 core canopied by 24 Cu, 44 Cl, 12 Cu and 12 Cl atoms that fulfill the tic@rco@oae@ico@ico penta-shell polyhedral configuration. By sharing the outmost-shell Cl atoms, the cuprofullerene chlorides are connected into 2D or 3D (snf net) frameworks. TD-DFT calculations reveal that the charge transfer from the outmost CuI and Cl to C60 core is responsible for their light absorption expansion to near-infrared region, implying anionic halogenation may be an effective strategy to tune the light absorption properties of metallofullerene materials.

A 1D Mixed-Valence Cuprofullerene Pyrazolate Polymer as a Semiconductor Material.

Polymeric {Cu6[(µ3-η2:η2:η2)2-C60](FPz)6Cl·3C6H5Cl}∞ [FPz = 4-(trifluoromethyl)pyrazolate], synthesized solvothermally with chlorobenzene as the solvent, is a doubly-connecting trans bis-adduct hexanuclear cuprofullerene that has copper in mixed valence. The compound is an example of a metallofullerene having semiconductivity character.

Regioisomeric core-shell cuprofullerene C60@Cu24.

The controlled synthesis of high-nuclear regioisomeric core-shell exohedral metallofullerenes (ExMFs) is challenging. Herein, we demonstrated the synthesis of regioisomeric core-shell cuprofullerene C60@CuI24 and its 3-D coordination polymer using heteroleptic ligands, realizing high-nuclear regioisomeric ExMFs and a polymeric ExMF structure.

Pressure-induced phosphorescence enhancement and piezochromism of a carbazole-based cyclic trinuclear Cu(i) complex.

Interest in piezochromic luminescence has increased in recent decades, even though it is mostly limited to pure organic compounds and fluorescence. In this work, a Cu3Pz3 (Cu3, Pz: pyrazolate) cyclic trinuclear complex (CTC) with two different crystalline polymorphs, namely 1a and 1b, was synthesized. The CTC consists of two functional moieties: carbazole (Cz) chromophore and Cu3 units. In crystals of 1a, discrete Cz-Cu3-Cu3-Cz stacking was found, showing abnormal pressure-induced phosphorescence enhancement (PIPE), which was 12 times stronger at 2.23 GPa compared to under ambient conditions. This novel observation is ascribed to cooperation between heavy-atom effects (i.e., from Cu atoms) and metal-ligand charge-transfer promotion. The infinite π-π stacking of Cz motifs was observed in 1b and it exhibited good piezochromism as the pressure increased. This work demonstrates a new concept in the design of piezochromic materials to achieve PIPE via combining organic chromophores and metal-organic phosphorescence emitters.

Luminescent polymorphic aggregates of trinuclear Cu(I)-pyrazolate tuned by intertrimeric CuNPy weak coordination bonds.

Five luminescent polymorphic aggregates of trinuclear Cu(i)-pyrazolate, namely [anti-Cu3L3]2 (1), [syn-Cu3L3·C2H5OH]2 (2), [anti-Cu3L3·C2H5OH]n (3), [anti-Cu3L3·0.5C7H8]n (4) and [syn-Cu3L3·C8H10]n (5) (HL = 4-(pyridin-4-ylthio)-3,5-dimethyl-1H-pyrazole), were reported. The trimeric Cu3L3 fragments present syn- and anti-conformations dependent on the dangled direction of 4-pyridyl groups on the two sides of the Cu3Pz3 plane (Pz = pyrazolate). Intertrimeric NPyCu weak coordination bonds associate these Cu3L3 fragments together to form dimeric or polymeric structures, which are further stabilized by crystallized solvent molecules or intertrimeric CuCu interactions. The solvated complexes (3-5) may be transformed into the unsolvated complex 1 by evacuation of the crystallized solvents upon heating. All these complexes emit from green to yellow under UV irradiation, which originated from the triplet excited states of metal to ligand charge transfer (3MLCT) mixed with intertrimeric CuCu interactions. This work provides a novel kind of supramolecular aggregate based on Cu3Pz3 beyond the classical π-acidbase adducts and metallophilicity-dependent dimers/oligomers.

Exohedral Cuprofullerene: Sequentially Expanding Metal Olefin Up to a C60@Cu24 Rhombicuboctahedron.

Exohedral cuprofullerenes with 6-, 12-, or 24-nuclearity were obtained by utilizing fluorocarboxylic/dicarboxylic acid under solvothermal conditions. The 24-nuclear molecule presents a C60@Cu24 core-shell structure with a rhombicuboctahedron Cu24 coated on the C60 core, representing the highest nuclearity in metallofullerene. The resultant complexes show an efficient absorption of visible light as opposed to the pristine C60. TD-DFT calculations revealed the charge transfer from Cu(I) and O atoms to the fullerene moiety dominates the photophysical process.

Coordination disk-type nano-Saturn complexes.

The first coordination disk-type nano-Saturn complexes, [Cu10(Mim)10]⊃C60 and [Cu10(Mim)10]⊃C70 (Mim = 2-methylimidazolate), were assembled under one-pot solvothermal conditions. The highest number of 30 C-Hπ interactions between the [Cu10(Mim)10] disk and the C60/C70 surfaces drives the formation of the nano-Saturns. The calculated interaction energy is much larger than that of most of the reported disk-type nano-Saturns. Different photoinduced charge/energy transfer mechanisms are present for both nano-Saturn systems to quench the intrinsic luminescence of the [Cu10(Mim)10] disk.

White Light from Blue Fluorescence and Sensitized Yellow Long-Afterglow Phosphorescence of o-Terphenyl in Its π-Acid···Base Adduct with Ag3Pz3.

White-light emission with CIE (0.32, 0.34) was realized for an o-terphenyl (oTP) molecule in its Ag3[3,5-(CF3)2Pz]3 (Pz = pyrazolate) sandwiching adduct, originating from the hybrid of fluorescence and sensitized long-afterglow phosphorescence of oTP. Density functional theory (DFT) and time-dependent DFT calculations revealed that heavy-atom effects of Ag play a crucial role in sensitization of the triplet of oTP, giving off its ultralong phosphorescence.

A luminescent edge-interlocked prismatic heteroleptic metallocage assembled through a ligand replacement reaction.

A luminescent edge-interlocked heteroleptic metallocage based on Cu3(pyrazolate)3 was prepared through a ligand replacement reaction from a homoleptic metallocage and a new ligand. Its structure was confirmed by XRD and MALDI-TOF mass spectrometry. Theoretical calculations revealed the new ligand was evidently responsible for the bathochromic shift of the optimal excitation. This work provides a heteroleptic strategy to regulate the interlocking fashion and photophysical mechanism of metallocages based on Cu3(pyrazolate)3.

Counteranion-Triggered and Excitation-Dependent Chemopalette Effect in a Supramolecular Dual-Emissive System Based on Cu3Pz3.

Three Cu3Pz3-based isostructural complexes (Cu3L3)2(CuX)2 (labeled as 1-ClO4, 1-NO3, and 1-Br, where X = ClO4-, NO3-, and Br-, respectively) were prepared by solvothermal reactions of an angular bifunctional pyridyl-pyrazole ligand, 4-(pyridin-4'-ylthio)-3,5-dimethyl-1 H-pyrazole ( HL), with Cu(ClO4)2, Cu(NO3)2, and CuBr, respectively. Pyrazolate (Pz) groups are highly specific to form planar trinuclear Cu3Pz3 units. Two Cu3L3 units are further connected by two CuX units through NPy-Cu-NPy (Py = 4-pyridyl) bonds to form an octanuclear chairlike molecule (Cu3L3)2(CuX)2, which then self-assembles through intertrimeric cuprophilicity to construct chainlike supraaggregates featuring two luminophores, [Cu3Pz3]2 and CuPy2X. With different counteranions (ClO4-, NO3-, and Br-), the complexes give off various emissions from red to green upon UV irradiation. 1-ClO4 and 1-NO3 show only low-energy (LE) orange (λemmax = 585 nm) and red (λemmax = 640 nm) emissions, while 1-Br exhibits excitation-dependent (260-360 nm) emissions from yellow to green due to variation in the relative intensities of two resolvable emissions, high energy (HE, λemmax = 520 nm) and LE (λemmax = 630 nm). The dual emissions are assigned to 3CC (LE states) based on excimeric [Cu3Pz3]2 units and 3XLCT/3MLCT (HE states) based on CuPy2X units. This work realizes a chemopalette effect through regulations of the counteranion and excitation energy in a dual-emissive system. It provides valuable insights into the nature of dual-emissive materials and the further investigation of the photophysical mechanism in such a system.

A luminescent supramolecular Cu2I2(NH3)2-sandwiched Cu3(pyrazolate)3 adduct as a temperature sensor.

A highly luminescent supramolecular Cu2I2(NH3)2-sandwiched Cu3(pyrazolate)3 adduct was reported as a temperature sensor. The adduct is stabilized by the synergy of intermolecular Cu3I (π acidbase), CuCu and NH interactions, to form a Cu8I2 cluster. The emission intensity exhibits a temperature-dependent effect in the solid state with a sensitivity of -0.685% K-1. DFT and TDDFT calculations revealed that the luminescence originates from the triplet state of Cu8I2 cluster-centered charge transfer (3CC).

Luminescent Cu4I4-Cu3(Pyrazolate)3 Coordination Frameworks: Postsynthetic Ligand Substitution Leads to Network Displacement and Entanglement.

Six daughter complexes based on two-dimensional (2-D) luminescent Cu4I4-Cu3Pz3 (Pz = pyrazolate) coordination networks, which exhibit an uncommon Cu4I4L3L' (L = pyridine; L' = acetonitrile, pyridine, pyrazine, 1,4-diazabicyclo[2.2.2]octane, triphenylphosphine, none) local configuration, were prepared through a postsynthetic modification method starting from a parent complex (L' = NH3). This work has successfully implemented the single-site substitution of Cu4I4-based coordination frameworks, which have rarely been reported for isolated Cu4I4-type compounds, by taking advantage of the solvent-assisted ligand substitution strategy recently developed in metal-organic framework (MOF) chemistry. Such a procedure not only resulted in the variation of local geometry in the Cu4I4 units but also led to interlayer network displacement and entanglement. Particularly, an interesting topological transformation (from 2-D to 2-D → 3-D interpenetration) occurred when linear bidentate linkers (e.g., pyrazine and 1,4-diazabicyclo[2.2.2]octane) are inserted between the 2-D layers. Moreover, the variation in the L' sites can effectively tune the emission colors, ranging from green to orange (λemmax 540-605 nm at room temperature). The photoluminescence origins are tentatively assigned to be a mixture of 3MLCT and 3XLCT, different from that of the well-studied isolated Cu4I4-type complexes.

Mechanically triggered fluorescence/phosphorescence switching in the excimers of planar trinuclear copper(I) pyrazolate complexes.

Luminescence mechanochromism of the well-known Cu3Pz3-type (Pz = pyrazolate) complexes is reported here, which is unusual for this family. Two types of new Cu3Pz3 complexes, namely Cu3(EBPz)3 (1; EBPz = ethyl-4'-benzoate-3,5-dimethylpyrazolate) and Cu3(MBPz)3 (polymorphs 2a-c; MBPz = methyl-4'-benzoate-3,5-dimethylpyrazolate), have been synthesized and characterized. Their crystal structures exhibit a similar chairlike dimer stacking supported by short Cu···Cu contacts, which would facilitate the formation of photoinduced excimers. The dual emission from the organic fluorophore and excimeric copper cluster phosphor is found to undergo mechanically induced intensity switching between their high-energy (HE) and low-energy (LE) bands. Specifically, the relative intensities of crystalline samples are HE > LE, while the ground solid samples show LE > HE, resulting in the overall emission color interchanging between bluish violet and red. This switching can be reversed by application of solvent to the ground samples, presumably due to recrystallization, and also by heating. TD-DFT calculations reveal that the emissive singlet ligand localized state (S1) and triplet cluster centered state (T8) lie close in energy (separated by a gap of 0.1788 eV), suggesting the feasibility of dual emission and the possibility of reverse intersystem crossing, consistent with the long fluorescent lifetimes (10(2) ns scale) of the HE bands.

Metallophilicity-driven dynamic aggregation of a phosphorescent gold(I)-silver(I) cluster prepared by solution-based and mechanochemical approaches.

We observed an unusual reversible aggregation process showing stimuli-responsive structural dynamics and optical changes attributed to the formation of a sandwich-like Au3-Ag-Au3 cluster, which can be synthesized through both solution and mechanochemical methods. Unlike many other heteronuclear gold-silver clusters, the affinity of two cyclic Au3 complexes and a Ag(I) ion is solely bound by ligand unsupported Au-Ag bonding. The assembly/disassembly behavior, further forming nanoaggregates, is controllable by adjusting the concentration of the solution. In the solid state, the insertion of Ag(I) ion can be implemented through a mechanochemical approach, accompanied by visual color changes and reversible luminochromism. Furthermore, an uncommon solid-liquid extraction is demonstrated, showing the uniqueness of this labile Au-Ag metallophilicity and hinting at the possibility of manipulating a bonding process through a heterogeneous route.

Luminescent metal-organic frameworks (MOFs) as a chemopalette: tuning the thermochromic behavior of dual-emissive phosphorescence by adjusting the supramolecular microenvironments.

Two classical copper(I)-cluster-based luminophores, namely, Cu4I4 and [Cu3Pz3]2 (Pz = pyrazolate), are immobilized in a supramolecular system through the formation of metal-organic framework (MOF) materials. This series of luminescent MOF materials, namely, [Cu4I4(NH3)Cu3(L1)3]n, [Cu4I4(NH2CH3)Cu3(L1)3]n, and [Cu4I4Cu3(L2)3]n (L1 = 3-(4-pyridyl)-5-(p-tolyl)pyrazolate; L2 = 3-(4-pyridyl)-5-(2,4-dimethylphenyl)pyrazolate), exhibit diverse thermochromism attributed to the relative functioning efficacy of the two coordination luminophores. Such an intriguing chemopalette effect is regulated by the different supramolecular microenvironments between the two-dimensional layers of these MOFs, and in particular, by the fine-tuned Cu-Cu distances in the excimeric [Cu3Pz3]2 luminophore. The structure-property elucidation of the thermochromic behavior allows one to understand these optical materials with unusual dual-emissive properties.

A high-symmetry coordination cage from 38- or 62-component self-assembly.

Artificial molecular architecture from a large number of subcomponents (>50) via self-assembly remains a formidable challenge for chemists. Reaction of 38 components [14 Ni(2+) and 24 N-methyl-1-(4-imidazolyl)methanimine] under solvothermal conditions reproducibly leads to the formation of a high-symmetry coordination cage. This polyhedral cage can also be obtained in high yield by self-assembly of 62 commercially available subcomponents (24 methylamine, 24 4-formylimidazole, and 14 Ni(2+)) under mild conditions involving synchronized formation of both dynamic covalent bonds and coordination bonds. Guest molecules (e.g., water, methylamine, and methanol) are randomly imprisoned in the cage.

When Cu4I4 cubane meets Cu3(pyrazolate)3 triangle: dynamic interplay between two classical luminophores functioning in a reversibly thermochromic coordination polymer.

A supramolecular dual emissive system incorporating two classical copper(I)-cluster-based luminophores, namely, Cu(4)I(4) and Cu(3)Pz(3) (Pz = pyrazolate), is reported. The targeted luminescent coordination polymer exhibits reversible thermochromism spanning from green to orange-red.