Construction of [(η5-C5Me5)MoS3Cu3]-Based Supramolecular Assemblies from the [(η5-C5Me5)MoS3(CuNCS)3]- Cluster Anion and Multitopic Ligands with Different Symmetries

Construction of cluster-based supramolecular wire and rectangle

Reactions of [Et₄N][Tp*WS₃(CuCl)₃] (1) (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) with 2 equiv. of AgOTf (OTf^- = trifluoromethanesulfonate) and 1 equiv. of several bidentate pyridine ligands including 2,5-bis(pyridine-4-yl)thiazolo[5,4-d]thiazole (L1), 2,7-di(pyridin-4-yl)-9H-fluorene (L2), 2,7-di(pyridin-4-yl)-9H-carbazole (L3), and 2,7-di(pyridin-4-yl)-9H-fluoren-9-one (L4) afforded four W/Cu/S cluster-based supramolecular compounds [(Tp*WS₃Cu₂Cl)₂(L1)] (2), {[(Tp*WS₃Cu₃)₂(μ-Cl)₂(μ₄-Cl)]₂(L2)₂}(OTf)₂ (3), {[(Tp*WS₃Cu₃)₂(μ-Cl)₂(μ₄-Cl)]₂(L3)₂}(OTf)₂ (4) and {[(Tp*WS₃Cu₃)₂(μ-Cl)₂(μ4-Cl)]₂(L4)₂}(OTf)₂ (5). Compounds 2-5 were characterized by elemental analysis, IR, UV-vis, ¹H NMR, and single-crystal X-ray diffraction analysis. The neutral cluster 2 behaves as a supramolecular wire constructed by L1 bridging two butterfly-shaped [Tp*WS₃Cu₂Cl] cores. The cluster cations of 3-5 contain two [(Tp*WS₃Cu₃)₂(μ-Cl)₂(μ₄-Cl)]⁺ cores linked by two L2, L3, or L4 ligands, which finally formed a cationic supramolecular rectangle. The third-order nonlinear-optical (NLO) properties of 3-5 in DMF were also investigated by Z-scan techniques and their NLO responses were enhanced compared to those of their precursor 1.

Heterobimetallic Cluster-Based Coordination Polymers: Assembly, Structures and Third-Order Nonlinear Optical Properties

Reactions of (NH₄ )₂ WS₄ with CuCN, CuCN/1,2-bis(4-pyridyl)propane (bppa) or [Cu(MeCN)₄ ]PF₆ /bppa under different reaction conditions afforded a set of two- or three-dimensional W/Cu/S cluster-based coordination polymers including {[Et₄ N]₂ [WS₄ Cu₄ (μ-CN)₂ (μ-I)₂ ]}_n (1), [WS₄ Cu₄ (μ-CN)₂ (bppa)₂ ]_n (2) and {[WS₄ Cu₄ (bppa)₄ ](PF₆ )₂ }_n (3), respectively. Compound 2 can be readily formed from reaction of 1 with bppa under solvothermal conditions. Compounds 1 and 2 feature two-dimensional networks with a "sql" topology, while 3 possesses a two-fold interpenetrated three-dimensional net with a rare "reo" topology. Compounds 1-3 in DMF exhibited different third-order nonlinear optical responses, and they all showed a reverse saturable absorption while 2 held a strong self-focusing effect.

Similarities and differences between Mn(II) and Zn(II) coordination polymers supported by porphyrin-based ligands: synthesis, structures and nonlinear optical properties

Four coordination polymers (CPs) Mn-TMPP (1), Zn-TMPP (2), Mn-THPP (3), and Zn-THPP (4) have been synthesized and characterized (H2TMPP = meso-tetrakis (6-methylpyridin-3-yl) porphyrin; H2THPP = meso-tetrakis (6-(hydroxymethyl) pyridin-3-yl) porphyrin). The one-dimensional (1D) chain compound 1 is formed via a head-to-tail connection of the Mn-TMPP unit, wherein the central Mn2+ features a square pyramidal geometry coordinated by four N atoms from the porphyrin skeleton and one additional N atom from an adjacent Mn-TMPP unit. Compound 2 features an octahedral Zn2+ center associated with four N atoms from the porphyrin skeleton to define the equatorial plane and two additional N donors at the axial positions to give a two-dimensional (2D) CP. The 1D chain of 1 and the 2D layer of 2 possess distinctive molecular structures but nearly identical molecular arrangements in their unit cells viewed along all three crystallographic axes. By contrast, Mn- and Zn-based CPs 3 and 4 supported by the THPP ligand share both identical molecular connectivities and crystal packing. In 3/4, each Mn/Zn center is chelated by four N donors of the porphyrin interior to define the equatorial plane of an octahedron, whose axial sites are occupied by two alcoholic OH groups from a pair of trans-located pyridinemethanol moieties. The third-order nonlinear optical properties of 1-4 investigated using the Z-scan technique at 532 nm revealed reverse saturable absorption and self-focusing effects for all four CPs, with hyperpolarizability values (γ) in the range 1.42 × 10-28 esu to 7.64 × 10-28 esu. These high γ values are comparable to the best porphyrin-based molecular assemblies, demonstrating potential for these materials in optical limiting applications.

Heavy chalcogenide-transition metal clusters as coordination polymer nodes

While metal-oxygen clusters are widely used as secondary building units in the construction of coordination polymers or metal-organic frameworks, multimetallic nodes with heavier chalcogenide atoms (S, Se, and Te) are comparatively untapped. The lower electronegativity of heavy chalcogenides means that transition metal clusters of these elements generally exhibit enhanced coupling, delocalization, and redox-flexibility. Leveraging these features in coordination polymers provides these materials with extraordinary properties in catalysis, conductivity, magnetism, and photoactivity. In this perspective, we summarize common transition metal heavy chalcogenide building blocks including polynuclear metal nodes with organothiolate/selenolate or anionic heavy chalcogenide atoms. Based on recent discoveries, we also outline potential challenges and opportunities for applications in this field.

Isoreticular Tp*–W–Cu–S cluster-based one-dimensional coordination polymers with an uncommon [Tp*WS3Cu2] + [Cu] combination and their third-order nonlinear optical properties

Three isoreticular W/Cu/S 1D coordination polymers show good third-order NLO performance.

Morphology-dependent third-order optical nonlinearity of a 2D Co-based metal-organic framework with a porphyrinic skeleton

A two-dimensional (2D) Co-based metal-organic framework (MOF) with porphyrinic skeleton forms crystalline plates, flower-shaped clusters, and ultrathin films under optimized conditions, including the use of polyvinylpyrrolidone (PVP) as a surfactant. Ultrathin films demonstrate the best solution-based third-order nonlinear optical properties, featuring a nonlinear transmittance (T) value of 0.54, absorption coefficient (α2) of 9.5 × 10-10 m W-1 and second hyperpolarizability (γ) value of 1.37 × 10-28 esu, which are slightly better than those of the flower-shaped clusters (T = 0.65, α2 = 7.0 × 10-10 m W-1; γ = 1.27 × 10-28 esu), but marginally better than those of the crystalline thin plates (T = 0.94, α2 = 2.4 × 10-10 m W-1; γ = 0.24 × 10-28 esu).

Evaluating the component contribution to nonlinear optical performances using stable [Ni4O4] cuboidal clusters as models

Cuboidal [Ni₄O₄]-based clusters are systematically studied with the purpose of evaluating the component contribution to the overall nonlinear optical performances.

Tungsten(VI)-Copper(I)-Sulfur Cluster-Supported Metal-Organic Frameworks Bridged by in Situ Click-Formed Tetrazolate Ligands

Six analogous two-dimensional (2D) [Tp*WS₃Cu₃]-based (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) networks, namely, {[(Tp*WS₃Cu₃)₂L₃](μ₃-N₃)}_n (2: L = 5-methyltetrazolate (Mtta); 3a: L = 5-ethyltetrazolate (Etta)) and {[(Tp*WS₃Cu₃)₂L₃]BF₄}_n (3b: L = Etta; 4: L = 5-propyltetrazolate (Ptta); 5: L = 5-butyltetrazolate (Btta); 6: L = 5-pentyltetrazolate (Petta)) were synthesized by reactions of [Et₄N][Tp*WS₃] (1), [Cu(CH₃CN)₄]BF₄, NaN₃, and NH₄BF₄ in different nitrile solvents (CH₃(CH₂)_nCN, n = 0, 1, 2, 3, and 4) under solvothermal conditions. In the structures of 2-6, each alkyl tetrazolate L as a bridging ligand was generated in situ from the "click" reaction between azide and nitrile. These 2D (6,3) networks support two types of voids wherein the pendant alkyl groups are accommodated. A tetrahedron cage-like cluster [Tp*W(μ₃-S)₃(μ₃-S')Cu₃]₄ (7) was also formed in some of the above reactions and can be readily separated by solvent extraction. The proportion of 7 increased with the elongation of the alkyl chains and finally became the exclusive product when heptylnitrile was employed. Further use of CuCN as a surrogate for [Cu(CH₃CN)₄]BF₄ with the aim of introducing additional CN bridges into the network led us to isolate a tetrazolate-free compound, {[Et₄N]{(Tp*WS₃Cu₃)[Cu₂(CN)_4.5]}₂·2PhCH₂CN}_n (8·2PhCH₂CN), a unique 2D network that features {(Tp*WS₃Cu₃)[Cu₂(CN)₅]}₂^2-, {(Tp*WS₃Cu₃)₃[Cu₃(CN)₇]₂[Cu(CN)₃]}^4-, and {(Tp*WS₃Cu₃)[Cu₄(CN)₉]}₂^6- ring subunits. Compounds 5-8 are soluble in DMF and exhibit a reverse saturable absorption and self-focusing third-order nonlinear optical (NLO) effect at 532 nm with hyperpolarizability γ values in the range of 4.43 × 10^-30 to 5.40 × 10^-30 esu, which are 400-500 times larger than that of their precursor 1. The results provide an interesting insight into the synergetic synthetic strategy related to the assembly of the [Tp*WS₃Cu₃]²⁺ cluster core, the "click" formation of the tetrazolate ligands, and the construction of the [Tp*WS₃Cu₃]²⁺ cluster-based 2D networks.

Diverse Tp*-Capped W-Cu-S Clusters from One-Pot Assembly Involving in Situ Thiolation of Phosphines

In the absence/presence of S8, the one-pot assembly of [Et4N][Tp*WS3] [1; Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] with [Cu(MeCN)4]PF6 and bis- or tetraphosphine ligands 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), and N,N,N',N'-tetrakis(diphenylphosphinomethyl)ethylenediamine (dppeda) produces six W-Cu-S clusters, namely, [(Tp*WS3Cu2Cl)2(dppe)] (2), [Tp*WS3Cu4(dppp)2(μ4-Cl)(μ-Cl)]PF6·MeCN (3·MeCN), [(Tp*WS3Cu3)2(μ4-Cl)(μ-Cl)2(dpppS2)] (4), [(Tp*WS3Cu2Cl)2(dppbS2)]·2MeCN·2H2O (5·2MeCN·2H2O), [(Tp*WS3Cu3Cl2)2(dppbS2)] (6), and [(Tp*WS3Cu3)2(Ph2PS2)3(μ6-Cl)0.5](PF6)0.5·0.75CH2Cl2 (7·0.75CH2Cl2). Compounds 2-7 are characterized by elemental analysis, IR, UV-vis, (1)H and (31)P{(1)H} NMR, electrospray ionization mass spectrometry, and X-ray crystallography. For 2, the dppe ligand bridges a pair of butterfly-shaped [Tp*WS3Cu2] cores to form a double-butterfly-shaped structure. For 4, the dppp ligand is susceptible toward S association and forms an in situ generated dpppS2 ligand, supporting an octanuclear double-half-open-cubane structure and contrasting an analogous system wherein a pentanuclear motorcycle-shaped cationic cluster 3 is formed with the absence of S8. A longer dppb ligand readily converts to S-based ligands in 5 and 6, subsequently serving as bridges between a pair of a butterfly-shaped (5) and nest-shaped (6) clusters. Further use of a tetraphosphine ligand, dppeda, in the cluster formation, with the presence of S8, leads to an unexpected ligand degradation to give the [Ph2PS2](-) anions. Three [Ph2PS2](-) anions juxtapose a pair of nest-shaped cluster cores to yield an octanuclear cluster, 7, featuring a cage to encapsulate μ6-Cl(-). The third-order nonlinear-optical (NLO) properties of 2-7 in N,N-dimethylformamide, investigated using a Z-scan technique at 532 nm, show that 2-6 have a reverse saturable absorption, while 7 has a notable saturable absorption. All of 2-7 exhibit a self-focusing effect with hyperpolarizability γ values in the range of 4.71 × 10(-30)-1.02 × 10(-29) esu, which are 440-1000 times higher than that of 1. The formation of 4-7 from 1 through the in situ thiolation of phosphine ligands presents a new approach to the design and assembly of the W-Cu-S clusters with interesting structural arrays and better NLO properties.

Rational construction of functional molybdenum (tungsten)–copper–sulfur coordination oligomers and polymers from preformed cluster precursors

Discrete Mo(W)–Cu–S clusters are used as precursors and building blocks for a diverse array of cluster-supported coordination oligomers and polymers.

Solvent effect-driven assembly of W/Cu/S cluster-based coordination polymers from the cluster precursor [Et4N][Tp*WS3(CuBr)3] and CuCN: isolation, structures and enhanced NLO responses

Solvent modulation of a W/Cu/S cluster and CuCN reaction system provides coordination polymers with enhanced nonlinear optical performances.