Article pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX-XXX
Luminescent Cu4I4−Cu3(Pyrazolate)3 Coordination Frameworks: Postsynthetic Ligand Substitution Leads to Network Displacement and Entanglement Shun-Ze Zhan,*,† Mian Li,† Ji Zheng,†,‡ Qiu-Juan Wang,† Seik Weng Ng,§ and Dan Li*,‡ †
Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou 515063, People’s Republic of China ‡ College of Chemistry and Materials Science, Jinan University, Guangzhou 510632, People’s Republic of China § The University of Nottingham Malaysia Campus, 43500 Semenyih, Selangor Darul Ehsan, Malaysia S Supporting Information *
ABSTRACT: 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, 1,4diazabicyclo[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 solventassisted 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 2D → 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.
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INTRODUCTION Luminescent copper(I) coordination complexes and clusters have gained much attention in the fields of molecular/ supramolecular photophysics and photochemistry due to their rich excited-state properties and practical applications,1 especially for the copper(I) halide family (e.g., Cu4I4-type compounds), owing to the contributions of Hardt, Ford, and many groups later.1a,2−4 Recently, these classical CuI-based compounds have been investigated systematically toward achieving high-performance hybrid lighting phosphors with excellent thermal and light stability,3 many of which exhibit one- to three-dimensional (1-D, 2-D, and 3-D) networked structures.2a Concerning solid-state lighting materials, it should be desirable to manipulate the spatial distribution of the luminophores and to modify the local functional sites while retaining the global network topology.5,6 Thanks to the recent development in metal−organic framework (MOF) chemistry, it is now possible to implement building block replacement for targeted applications through postsynthetic solvent-assisted ligand substitution7 and metal metathesis8 strategies. Our group has been interested continuously in copper(I) clusters, such as copper(I) halides2a and copper(I) pyrazolates,9 © XXXX American Chemical Society
in isolated and networked systems, which involve intra- and/or intermolecular Cu−Cu interactions and exhibit tunable solidstate phosphorescence. Recently, we succeeded in incorporating two classical copper(I) cluster luminophores, i.e. Cu4I4 and [Cu3Pz3]2 (Pz = pyrazolate) (Figure 1), within a crystalline
Figure 1. Two classical copper(I) clusters serving as building blocks in 1·NH3: (a) Cu4I4 unit with NH3 as an anchoring ligand; (b) dimeric [Cu3Pz3]2 unit with a staggered stacking mode. Color codes: red, Cu; blue, N; black, C; purple, I; gray, H. Cu−Cu interactions are shown in green. Received: August 23, 2017
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DOI: 10.1021/acs.inorgchem.7b02144 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
Figure 2. (a) Scheme showing the postsynthetic solvent-assisted reaction to yield complexes 3−5 from the parent complex 1·NH3 (highlighting the Cu4I4L3L′ local configuration). (b) Photographs (amplified 40 times) showing the crystals of complexes 3−5 under daylight (brighter background) and 365 nm UV light (darker background), respectively. The central structure illustrates the top view of the double-layer packing in the parent and daughter complexes.
supramolecular dual-emissive system.4 Three two-dimensional binary-cluster-based coordination networks, namely, [(Cu4I4)(NH3)Cu3(L1)3]n (1·NH3),4a [(Cu4I4)(NH2CH3)Cu3(L1)3]n (1·NH2CH3), and [(Cu4I4)Cu3(L2)3]n (2)4b (L1 = 3-(4pyridyl)-5-(p-tolyl)pyrazolate; L2 = 3-(4-pyridyl)-5-(2,4dimethylphenyl)pyrazolate), were prepared from a symmetryguided self-assembly approach. Subsequently, we attempted to prepare more compounds in this family of Cu4I4−Cu3Pz3 coordination networks by introducing other anchoring ligands in place of the coordinated NH3 (see Figure 1a) or NH2CH3.4 However, direct synthesis did not succeed; therefore, we sought a postsynthetic route by taking advantage of such a method developed in MOF chemistry.7,8 Starting from the parent complex 1·NH3,4a we have selected some monodentate (e.g., CH3CN and pyridine (Py)) and bidentate (e.g., pyrazine (Pyz) and 1,4diazabicyclo[2.2.2]octane (DABCO)) N-donor ligands, as well as a P-donor ligand (triphenylphosphine (PPh3)), for running the postsynthetic ligand substitution reactions. In the p r e s e n t w o r k , s i x d a u g h t er c o m p le x e s , n a m e l y , [Cu 4 I 4 Cu 3 (L1) 3 ] n (3), {[Cu 4 I 4 ·(CH 3 CN)Cu 3 (L1) 3 ]· CH 3 CN} n (3·CH 3 CN), [Cu 4 I 4 ·(Py)Cu 3 (L1) 3 ] n (3·Py), [Cu 4 I 4 ·(Pyz) 1 / 2 Cu 3 (L1) 3 ] n (4·Pyz), [Cu 4 I 4 ·(DABCO)1/2Cu3(L1)3]n (4·DABCO), and [Cu4I4·(PPh3)Cu3(L1)3]n (5·PPh3), are obtained through solvent-assisted ligand substitution (Figure 2). They give colorful emissions ranging from green to orange (λemmax 540−605 nm at room temperature), dependent on the variation in L′. The photoluminescence origins are tentatively assigned to be a mixture of 3MLCT and 3 XLCT.
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helium as cooling medium (Advanced Research Systems). The corrections of excitation and emission for the detector response were performed ranging from 200 to 900 nm. The data were analyzed by iterative convolution of the luminescence decay profile with the instrument response function using the software package provided by Edinburgh Instruments. Lifetime data were fitted with biexponential decay functions. The goodness of the nonlinear least-squares fit was judged by the reduced χ2 value (
