Pseudohalide Ions as Ligands to Tune Architecture and Luminescence of Polymetallic CU(I) Assemblies.

The reaction of preassembled Cu(I) bimetallic units {Cu2(dppm)2} and {Cu2(dppa)2} (dppm: bis(diphenylphosphino)methane and dppa: bis(diphenylphosphino)amine) with pseudohalide linkers (azido, dicyanamide, and tricyanomethanide) allows for the quantitative and selective preparation of three discrete tetrametallic metallacycles of formula [Cu4(µ2-dppm)4(N3)2](PF6)2, [Cu4(µ2-dppm)4(N(CN)2)2](PF6)2, and [Cu4(µ2-dppm)4(C(CN)3)4]. To explore further the impact of the linker on the architecture and dimensionality of the molecular edifice, the study was extended to more sophisticated tetradentate cyanocarbanion ligands (tcnsMe-: 2-(methylthio)-1,1,3,3-propanetetracarbonitrile and tcnsEt-: 2-(ethylthio)-1,1,3,3-propanetetracarbonitrile). Three ladder-like one-dimensional coordination polymers and an octametallic metallacycle have been obtained. The careful comparison of the metric and geometrical intramolecular and intermolecular parameters observed in this series of seven derivatives allows for rationalization of their molecular architectures. The subtle balance between the length and steric hindrance of the ligand and the formation of noncovalent interaction networks greatly influences the topology and dimensionality of the resulting assemblies and will be discussed hereafter. The photophysical properties of these seven polymetallic Cu(I) compounds have also been also studied.

Statistical Analysis of Copper(I) Iodide and Bis(Diphenylphosphino)alkane-Based Complexes and Coordination Polymers.

The prediction of the metal cluster within a coordination polymer or complex, as well as the dimensionality of the resulting polymer or complex (i.e., 0D, 1D, 2D, or 3D), is often challenging. This is the case for Ph2P(CH2)mPPh2 ligands (1 ≤ m ≤ 8) and CuX salts, particularly for X = I. This work endeavors a systematic statistical analysis combining studies in the literature and new data, mapping the nature of the resulting CuI aggregates with eight different diphoshphines in 2:1, 3:2, 1:1, 2:3, and 1:2 CuI:Ph2P(CH2)mPPh2 molar ratios as a function of m, which lead to either pure products or mixtures. Several trends are made relating stoichiometry and chain length to the CuI cluster formed (i.e., globular vs. quasi-planar). Four new X-ray structures were determined: [Cu3I2(L1)3]I, Cu3I3(L2)2, Cu2I2(L6)2, and Cu4I4(L8)2, where m is, respectively, 1, 2, 6, and 8, in which the CuxIy central aggregates adopt triangular bipyramid, diamond, rhomboid, and cubane shaped motifs, respectively. Photophysical measurements assisted the establishment of trends considering the paucity of the crystallographic structures. During this study, it was also found that the 0D-complex Cu2I2(Ph2P(CH2)5PPh2)2 exhibits thermally activated delayed fluorescence.

Impact of Intermolecular Non-Covalent Interactions in a CuI 8 PdII 1 Discrete Assembly: Conformers' Geometries and Stimuli-Sensitive Luminescence Properties.

A new highly solid-state luminescent phase of a previously reported weakly luminescent CuI 8 PdII 1 dicationic assembly is reported revealing the high geometrical versatility of this moiety that importantly alters its luminescent properties. This very minor new species Bc is based on a different conformer scaffold than the one encountered in the previously reported Bo form and, essentially differs from Bo by displaying shorter CuI -CuI intermetallic distances. DFT calculations allow concluding that the predominance in the solid-state of the weakly luminescent and less stable Bo phase is due to the extra stability induced by a larger number of intermolecular non-covalent π-CH interactions in its crystalline packing and not by the intrinsic stability of the CuI 8 PdII 1 dicationic moiety. Calculations also revealed that a more stable conformation Bcalc is expected in vacuum, which bears a different distribution of CuI -CuI intermetallic distances than the dications in Bo and Bc phases. Taking into account that the geometrical alterations are associated to drastic changes of luminescence properties, this confer to the CuI 8 PdII 1 assembly high potentiality as stimuli-sensitive luminescent materials. Indeed, by applying mechanical or thermal stress to samples of Bo phase, new phases Bg and Bm , respectively, were obtained. Alterations of the solid-state photophysical properties of these new species compared to those recorded for Bo are reported together with a combined experimental and computed study of the structures/properties relationships observed in these phases.

Structural and Luminescence Properties of Anthracene- and Biphenyl-Based Lanthanide Bisphosphonate Ester Coordination Polymers.

Coordinative networks containing lanthanide ions attached via phosphonate ester functionalities provide remarkable luminescence properties. On the basis of ditopic phosphonic ester ligands with biphenylene and 9,10-anthracenylene bridges, a series of compounds with formal composition {[M(NO3)3]L} n or {[M(NO3)3]2(L1)3} n (L = C28H40O6P2; L1 = C26H40O6P2) with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y have been synthesized, structurally characterized, and the luminescence behavior was explored in the visible and NIR spectral regions, where applicable. In contrast to closely related networks based on biphenyl bisphosphonate esters from previous work, no evidence for ligand-to-metal energy transfer could be observed, despite strong near-infrared emission in some cases. Unique behavior is found for the Eu derivative with the 9,10-anthracenylene bridge, which is nonemissive, showing neither ligand- nor metal-based emission.

Adaptive Coordination-Driven Supramolecular Syntheses toward New Polymetallic Cu(I) Luminescent Assemblies.

A thermally activated delayed fluorescence (TADF) tetrametallic Cu(I) metallacycle A behaves as a conformationally adaptive preorganized precursor to afford, through straightforward and rational coordination-driven supramolecular processes, a variety of room-temperature solid-state luminescent polymetallic assemblies. Reacting various cyano-based building blocks with A, a homometallic Cu(I) 1D-helical coordination polymer C and Cu8M discrete circular heterobimetallic assemblies DM (M = Ni, Pd, Pt) are obtained. Their luminescence behaviors are studied, revealing notably the crucial impact of the spin-orbit coupling offered by the central M metal center on the photophysical properties of the heterobimetallic DM derivatives.

Can Coordination-Driven Supramolecular Self-Assembly Reactions Be Conducted from Fully Aliphatic Linkers?

The reaction between a preassembled CuI bimetallic molecular clip with a short intermetallic distance and a series of fully aliphatic cyano-capped ditopic linkers with increasing lengths was investigated. It is shown that, depending on the length of the ditopic linkers, the rational design of unprecedented supramolecular compact metallacycles containing fully aliphatic walls is possible. The specific preorganized molecular arrangement of the molecular clip used favors stabilizing interlinker London dispersion interactions, which allow, as the length of the linkers increases, the selective formation of discrete compact metallacycles at the expense of 1D coordination polymers. The generalizability of this approach was demonstrated by the reaction of fully aliphatic cyano-capped linkers with two other types of preassembled CuI bimetallic molecular clips that also had short intermetallic distances.

Hexalanthanide Complexes as Molecular Precursors: Synthesis, Crystal Structure, and Luminescent and Magnetic Properties.

Reaction of hexanuclear octahedral molecular precursors with a 3-chlorobenzoate ligand affords an unprecedented family of isostructural polylanthanide complexes via solvothermal and microwave-assisted syntheses in an acetonitrile medium. The general chemical formula of the compounds that constitute this series is {[Ln6(µ3-OH)2(H2O)2(NO3)2(3-cb)14]·(CH3CN)4}, where 3-cb- stands for 3-chlorobenzoate and Ln = Eu, Tb, Dy, Ho, Er, or Y. The crystal structure, solubility, and magnetic and luminescent properties of these complexes have been studied. The luminescent properties evidence that the composition of the hexalanthanide precursor is preserved during the synthetic process that is of particular interest for cases in which heterolanthanide complexes are targeted.

Supramolecular assembly of a phosphole-based moiety into nanostructures dictated by alkynylplatinum(ii) terpyridine complexes through non-covalent Pt···Pt and π-π stacking interactions: synthesis, characterization, photophysics and self-assembly behaviors.

A new class of platinum(ii) terpyridine complexes with a phosphole-derived bridging alkynyl ligand have been prepared. The X-ray crystal structure of complex 2 has been determined, and reveals a polymeric zig-zag chain structure with the existence of π-π stacking interactions. The photophysical properties have also been studied, with 3MLCT/3LLCT phosphorescence exhibited in degassed CH2Cl2; the energy of which is varied by the π-conjugation of the terpyridine ligands. The solvent-induced assembly of complex 1 has been studied. The incorporation of hydrophobic hydrocarbon chains has been shown to play an important role in assisting the formation of self-assembled nanostructures via Pt···Pt, π-π stacking and hydrophobic-hydrophobic interactions. It has been established that an isodesmic growth mechanism operates in polar media to give nanospheres, while fibrous networks originate from the self-assembly of the complexes in non-polar media, predominantly driven by π-π stacking interactions.

Coordination-Driven Syntheses of Compact Supramolecular Metallacycles toward Extended Metallo-organic Stacked Supramolecular Assemblies.

One important concept associated with supramolecular chemistry is supramolecular self-assembly, which deals with the way discrete individual components interact via intermolecular interactions in order to build, upon their spontaneous association, high order functional assemblies. The accumulation of these very simple and localized noncovalent interactions (such as H-bonding, dipole-dipole, hydrophobic/hydrophilic, van der Waals, π-π, π-CH, etc.) is ubiquitous in the complexity of natural systems (such as DNA, proteins, membranes, micelles, etc.). It can also be transposed to the directed synthesis of intricate artificial scaffolds, which have anticipated geometries and properties. Among the synthetic strategies based on this concept, coordination-driven supramolecular chemistry uses the robust, reversible, and directional metal-to-ligand coordinative bond to build discrete metallo-supramolecular architectures. Within the last two decades, coordination-driven supramolecular chemistry has proved to be one of the most powerful contemporary synthetic approaches and has provided a significant number of increasingly complex supramolecular assemblies, which have predetermined sizes and geometries. While much focus has been devoted to architectures bearing internal cavities for host-guest chemistry or to generate specific reactivity, particular attention can also be paid to compact supramolecular assemblies given that their specific structures are characterized by peculiar synthetic guiding rules as well as by alternative long-range self-assembling properties. This Account describes how a preassembled CuI bimetallic clip bearing short intermetallic distances can be used as a U-shaped molecular clip to give general and versatile access to a large variety of original compact supramolecular metallacycles. When this CuI precursor is reacted with various cyano-capped ditopic linkers that have increasing lengths and complexities, specific effects guiding the selective and straightforward syntheses of such compact supramolecular objects are highlighted. Whereas a subtle compromise between the length of the ditopic linkers and the steric bulk of the molecular clip appears to be a purely stereogeometric preliminary parameter to master, lateral interlinker interactions (π-π stacking interactions or aurophilic interactions depending on the nature of the internal cores of the linkers) can circumvent these constraints regardless of the length of the linkers and allow the selective formation of new compact supramolecular structures. Generally, such derivatives presented a strong tendency to self-assemble in the solid state due to inter-supramolecule interactions. This approach thus opens a new door toward molecular materials having an attractive solid state structure for potential applications related to charge carrier mobility and luminescence properties. These compact supramolecular assemblies can therefore be considered as original secondary binding units directing the predictive preparation of such extended networks. The on-purpose design of original building blocks bearing specific cores allowed the formation of new compact supramolecular metallacycles such as "U-shaped" π-stacked assemblies or "pseudodouble paracyclophanes". Similarly, the control of the secondary structure of one-dimensional coordination polymers alternating π-stacked compact supramolecular metallacycles was also conducted. The results that are discussed in this Account illustrate how the rational design of both preassembled polymetallic precursors bearing short intermetallic distances and ditopic linkers able to induce cumulative lateral weak interactions can implement the general synthetic guiding rules of coordination driven supramolecular chemistry. This opens perspectives to use such compact supramolecular assemblies as secondary building blocks for the design of long-range organized functional molecular materials that have predictable architectures and targeted properties.

Self-Assembly of Reactive Linear Cu3 Building Blocks for Supramolecular Coordination Chemistry and Their Reactivity toward E(n) Ligand Complexes.

This study describes the selective synthesis of linear, trinuclear, halide-bridged Cu(I) complexes [Cu3(µ-X)2(µ-dpmp)2(MeCN)2](+) (1a: X = Cl; 1b: X = Br; 1c: X = I) stabilized by the tridentate dpmp ligand obtained by self-assembly reactions in THF/MeCN. Upon drying, the MeCN ligands can be removed and the complexes are transformed to the reactive parent trinuclear [Cu3(µ-X)2(µ-dpmp)2](+) (2a-c) building blocks with two vacant coordination sites on the terminal Cu atoms. Another synthesis in CH2Cl2 directly yields 2a-c. Additionally, two related isomeric compounds, 2a* and 2c*, and two CH2Cl2-ligated complexes, [Cu3(µ-X)2(µ-dpmp)2(CH2Cl2)2](+) (X = Br (3b), I (3c)), were structurally characterized. The frameworks of the cationic [Cu3(µ-X)2(µ-dpmp)2](+) complexes are stable in solution at low temperatures and show dynamic coordination behavior at elevated temperatures, indicated by new signals arising in the (31)P{(1)H} NMR spectra. This evolution cannot be shifted back by decreasing the temperature again. However, cationic [Cu3(µ-X)2(µ-dpmp)2](+) (X = Cl, Br, I) complexes can be obtained selectively in the solid state upon crystallization. Although reactions of 2a-c with complexes [{CpMo(CO)2}2(µ,η(2):η(2)-E2)] (E = P (A1), As (A2)) led to unsymmetrically substituted [Cu3(µ-X)2(µ-dpmp)2(η(1)-L)](+) (4a-c: X = Cl-I, L = A1; 5: X = Cl, L = A2) complexes, reactions with the cyclo-P3 complex [CpMo(CO)2(η(3)-P3)] (B) afforded zigzag chain polymers [Cu3(µ-X)2(µ-dpmp)2(µ,η(1):η(1)-B)]n[BF4]n (6a: X = Cl; 6b: X = Br) and symmetrically substituted complex [Cu3(µ-I)2(µ-dpmp)2(η(1)-B)2](+) (7). Reactions of 2a-c with cyclo-E5 complexes [Cp*Fe(η(5)-E5)] (E = P (C1), As (C2)) led to the isolation of one-dimensional coordination polymers [Cu3(µ-X)2(µ-dpmp)2(µ,η(1):η(1)-L)]n[BF4]n (8a-b: X = Cl-Br, L = C1; 9: X = Cl, L = C2) and symmetrically substituted complex [Cu3(µ-I)2(µ-dpmp)2(η(1)-C1)2](+) (10). All products exhibit a trinuclear, cationic [Cu3(µ-X)2(µ-dpmp)2](+) complex as the central structural motif. Variation of the intramolecular Cu-Cu distances inside the Cu3 complexes is discussed, and supporting DFT computations for the model complex [Cu3(µ-Cl)2(dmmp)2{(η(1)-A1)}](+) (4a') are presented.

Bimetallic Gold(I) Complexes with Ethynyl-Helicene and Bis-Phosphole Ligands: Understanding the Role of Aurophilic Interactions in their Chiroptical Properties.

Monometallic gold(I)-alkynyl-helicene complexes (1 a,b) and bimetallic gold(I)-alkynyl-helicene architectures featuring the presence (2 a,b) or absence (3 a,b) of aurophilic intramolecular interactions were prepared by using different types of phosphole ligands (mono-phosphole L1 or bis-phospholes L2,3). The influence of the Au(I) d(10) metal center(s) on the electronic, photophysical, and chiroptical properties of these unprecedented phosphole-gold(I)-alkynyl-helicene complexes was examined. Experimental and theoretical results highlight the importance of ligand-to-ligand-type charge transfers and the strong effect of the presence or absence of Au(I) -Au(I) interactions in 2 a,b.

Organometallic polyphosphorus and -arsenic ligands as linkers between pre-assembled linear Cu(I) fragments.

A simple and straightforward synthesis of a new linear trinuclear Cu(I) cluster with polyphosphine ligands is presented. The reaction of this pre-organized Cu3 precursor with En ligand complexes (E = P, As; n = 2, 5) affords discrete complexes exhibiting end-on η(1)-coordination of the E2 ligands or one-dimensional coordination polymers featuring σ-1,3-bridging E5 rings, respectively.

Dissymmetrical U-shaped π-stacked supramolecular assemblies by using a dinuclear Cu(I) clip with organophosphorus ligands and monotopic fully π-conjugated ligands.

Reactions between the U-shaped binuclear Cu(I) complex A that bears short metal-metal distances and the cyano-capped monotopic π-conjugated ligands 1-5 that carry gradually bulkier polyaromatic terminal fragments lead to the formation of π-stacked supramolecular assemblies 6-10, respectively, in yields of 50-80 %. These derivatives have been characterized by multinuclear NMR spectroscopic analysis and X-ray diffraction studies. Their solid-state structures show the selective formation of U-shaped supramolecular assemblies in which two monotopic π-conjugated systems present large (6, 7, and 9) or medium (8 and 10) intramolecular π overlap, thus revealing π-π interactions. These assemblies self-organize into head-to-tail π-stacked dimers that in turn self-assemble to afford infinite columnar π stacks. The nature, extent, and complexity of the intermolecular contacts within the head-to-tail π-stacked dimer depend on the nature of the terminal polyaromatic fragment carried by the cyano-capped monotopic ligand, but it does not alter the result of the self-assembling process. These results demonstrate that the dinuclear molecular clip A that bears short metal-metal distances allows selective supramolecular assembly processes driven by the formation of intra- and intermolecular short π-π interactions in the resulting self-assembled structures; thus, demonstrating that their shape is not only dictated by the symmetry of the building blocks. This approach opens perspectives toward the formation of extended π-stacked columns based on dissymmetrical and functional π-conjugated systems.

Phosphorus centers of different hybridization in phosphaalkene-substituted phospholes.

Phosphole-substituted phosphaalkenes (PPAs) of the general formula Mes*P=C(CH(3))-(C(4)H(2)P(Ph))-R 5 a-c (Mes*=2,4,6-tBu(3)Ph; R=2-pyridyl (a), 2-thienyl (b), phenyl (c)) have been prepared from octa-1,7-diyne-substituted phosphaalkenes by utilizing the Fagan-Nugent route. The presence of two differently hybridized phosphorus centers (σ(2) ,λ(3) and σ(3) ,λ(3)) in 5 offers the possibility to selectively tune the HOMO-LUMO gap of the compounds by utilizing the different reactivity of the two phosphorus heteroatoms. Oxidation of 5 a-c by sulfur proceeds exclusively at the σ(3) ,λ(3) -phosphorus atom, thus giving rise to the corresponding thioxophospholes 6 a-c. Similarly, 5 a is selectively coordinated by AuCl at the σ(3),λ(3) -phosphorus atom. Subsequent second AuCl coordination at the σ(2),λ(3) -phosphorus heteroatom results in a dimetallic species that is characterized by a gold-gold interaction that provokes a change in π conjugation. Spectroscopic, electrochemical, and theoretical investigations show that the phosphaalkene and the phosphole both have a sizable impact on the electronic properties of the compounds. The presence of the phosphaalkene unit induces a decrease of the HOMO-LUMO gap relative to reference phosphole-containing π systems that lack a P=C substituent.

A tetradentate metalloligand: synthesis and coordination behaviour of a 2-pyridyl-substituted cyclobutadiene iron complex.

The salt [K([18]crown-6){Cp*Fe(η(4)-C4py4)}] (K1, py = 2-pyridyl, Cp* = C5Me5) is accessible by the reaction of an iron(0) naphthalene precursor and bis(2-pyridyl)acetylene. Cyclic voltammetry and preparative investigations demonstrate the electron-rich nature of K1, which is reversibly oxidized to neutral [Cp*Fe(η(4)-C4py4)] (1) at a low potential. The first coordination studies with iron(II) and zinc(II) chloride show that all four 2-pyridyl units may be employed for metal coordination.

Chiroptical properties of carbo[6]helicene derivatives bearing extended π-conjugated cyano substituents.

New carbo[6]helicene derivatives grafted with π-conjugated cyano-phenyl arms were synthesized in enantiopure forms and their π-conjugation examined by UV-vis spectroscopy. The influence of the π-conjugation on the circular dichroism spectra and molar rotations is discussed based on comparing experimental data with results from quantum-chemical calculations. The results highlight the fact that increasing the spatial extension of the π-system in a helicene molecule is an efficient way of increasing its molar rotation.

Syntheses of Cu(I) polymetallic assemblies from reaction of ligands bearing the 2,5-bis(2-pyridyl)phosphole fragment with Cu(II) precursors.

Upon reaction with ligands A, 1 and 3 bearing the 2,5-bis(2-pyridyl)phosphole fragment, an unexpected conversion of Cu(II) metal centers to Cu(I) centers is observed affording either bimetallic complexes bearing a bridging phosphane coordination mode or hexametallic metallacycles.

Synthesis of small tetranuclear Cu(I) metallacycles based on bridging pseudohalogenide ions.

Three new 'short' metallacycles are selectively obtained from the reaction of a bimetallic Cu(I) 'U-shape' molecular clip with, respectively, the cyano CN(-), tricyanomethanide C(CN)(3)(-), and azido N(3)(-) pseudohalogenide ions. These supramolecular assemblies have been characterized by spectroscopic methods, single-crystal X-ray diffraction, and elemental analysis. The single-crystal X-ray structures of these complexes reveal no short contact interaction between the pseudohalogenide ions within these self-assembled structures despite the short Cu(I)···Cu(I) distances within the molecular clips. The formation of these discrete metallacycles is rationalized by analyzing the structural features of the Cu(I) 'U-shape' molecular clip.

Rhenium complexes bearing phosphole-pyridine chelates: simple molecules with large chiroptical properties.

The synthesis and chiroptical properties of chiral rhenium complexes bearing mono- or di-topic phosphole ligands are described.