A Gold Quartet Framework with Reversible Anisotropic Structural Transformation Accompanied by Luminescence Response

Abstract

•Cluster assembly via post-synthetic modification of click-reaction-induced CCT•C4-symmetric hierarchical chiral gold quartet framework was realized•Pump-fill process of gases gives an anisotropic structural transformation•The reversible SCSC structural transformation is accompanied by luminescence change As the traditional top-down approach is reaching its limit, the bottom-up approach has been proved to be an efficient strategy for fabricating ordered, sophisticated, and functional materials through hierarchical supramolecular self-assembly. Based on their controllable configurations and structure-dependent properties, nanospecies with atom-precise structures can serve as ideal building blocks for bottom-up synthesis. The construction of functional materials using nanostructures represents a challenging area of research. Here, we report a bottom-up-constructed luminescent chiral superstructure that shows stimuli-responsive luminescence change. This work not only provides a new strategy for the construction of stimuli-responsive materials but also highlights the versatility of gold(I) nanoclusters in hierarchical cluster framework assembly. Hierarchy and chirality are the fundamental characteristics of biomolecules. Chemistry on hierarchical self-assembly and spontaneous symmetry breaking helps to uncover the mechanism of living activities and the origin of chirality in nature. Herein, we describe a chiral gold quartet framework (GQF) with C4-symmetric structure hierarchically aggregated from an achiral anionic [Au10(dpptrz)4S4]2− (dpptrz-Au10), which was acquired via click-reaction-induced and Au(I)⋅⋅⋅Au(I)-interaction-directed cluster-to-cluster transformation (CCT) from the rationally designed [(dppa)6Au18S8]2+ (dppa-Au18). Inter-cluster hydrogen bonding and alkali ion coordination were observed to assist the hierarchical self-assembly and chiral self-organization of the GQF. Upon exposing the crystal to vacuum, the bottom-up constructed GQF showed an anisotropic structural transformation accompanied by a visual luminescence change in a single-crystal-to-single-crystal (SCSC) manner that became reversible upon removal of vacuum. This research largely advances the potential of polynuclear gold(I)-sulfido clusters in hierarchical self-assembly and luminescent materials. Hierarchy and chirality are the fundamental characteristics of biomolecules. Chemistry on hierarchical self-assembly and spontaneous symmetry breaking helps to uncover the mechanism of living activities and the origin of chirality in nature. Herein, we describe a chiral gold quartet framework (GQF) with C4-symmetric structure hierarchically aggregated from an achiral anionic [Au10(dpptrz)4S4]2− (dpptrz-Au10), which was acquired via click-reaction-induced and Au(I)⋅⋅⋅Au(I)-interaction-directed cluster-to-cluster transformation (CCT) from the rationally designed [(dppa)6Au18S8]2+ (dppa-Au18). Inter-cluster hydrogen bonding and alkali ion coordination were observed to assist the hierarchical self-assembly and chiral self-organization of the GQF. Upon exposing the crystal to vacuum, the bottom-up constructed GQF showed an anisotropic structural transformation accompanied by a visual luminescence change in a single-crystal-to-single-crystal (SCSC) manner that became reversible upon removal of vacuum. This research largely advances the potential of polynuclear gold(I)-sulfido clusters in hierarchical self-assembly and luminescent materials. Gold was known to be a precious coinage metal in ancient days with the characteristics of nobility and stability.1Schmidbaur H. Gold—Progress in Chemistry, Biochemistry and Technology. John Wiley & Sons Ltd, 1999Google Scholar In recent decades, the rapid development of transition-metal chemistry and the awareness of gold⋅⋅⋅gold interactions (also known as aurophilic interactions) have largely boosted the growth of gold chemistry.1Schmidbaur H. Gold—Progress in Chemistry, Biochemistry and Technology. John Wiley & Sons Ltd, 1999Google Scholar, 2Schmidbaur H. Schier A. Aurophilic interactions as a subject of current research: an up-date.Chem. Soc. Rev. 2012; 41: 370-412Crossref PubMed Google Scholar, 3Pyykkö P. Strong closed-shell interactions in inorganic chemistry.Chem. Rev. 1997; 97: 597-636Crossref PubMed Scopus (2245) Google Scholar, 4Puddephatt R.J. Macrocycles, catenanes, oligomers and polymers in gold chemistry.Chem. Soc. Rev. 2008; 37: 2012-2027Crossref PubMed Scopus (182) Google Scholar, 5Che C.-M. Lai S.-W. Structural and spectroscopic evidence for weak metal-metal interactions and metal-substrate exciplex formations in d10 metal complexes.Coord. Chem. Rev. 2005; 249: 1296-1309Crossref Scopus (253) Google Scholar, 6Yam V.W.-W. Au V.K.-M. Leung S.Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes.Chem. Rev. 2015; 115: 7589-7728Crossref PubMed Scopus (1064) Google Scholar, 7Gimeno M.C. Laguna A. Chalcogenide centred gold complexes.Chem. Soc. Rev. 2008; 37: 1952-1966Crossref PubMed Scopus (103) Google Scholar, 8Yam V.W.-W. Cheng E.C.-C. Highlights on the recent advances in gold chemistry—a photophysical perspective.Chem. Soc. Rev. 2008; 37: 1806-1813Crossref PubMed Scopus (452) Google Scholar Among the gold family, polynuclear gold(I)-chalcogenido clusters bearing Au(I)⋅⋅⋅Au(I) interactions6Yam V.W.-W. Au V.K.-M. Leung S.Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes.Chem. Rev. 2015; 115: 7589-7728Crossref PubMed Scopus (1064) Google Scholar, 7Gimeno M.C. Laguna A. Chalcogenide centred gold complexes.Chem. Soc. Rev. 2008; 37: 1952-1966Crossref PubMed Scopus (103) Google Scholar, 8Yam V.W.-W. Cheng E.C.-C. Highlights on the recent advances in gold chemistry—a photophysical perspective.Chem. Soc. Rev. 2008; 37: 1806-1813Crossref PubMed Scopus (452) Google Scholar of bonding energy similar to that of hydrogen bonding2Schmidbaur H. Schier A. Aurophilic interactions as a subject of current research: an up-date.Chem. Soc. Rev. 2012; 41: 370-412Crossref PubMed Google Scholar, 3Pyykkö P. Strong closed-shell interactions in inorganic chemistry.Chem. Rev. 1997; 97: 597-636Crossref PubMed Scopus (2245) Google Scholar have attracted increasing research interest in recent decades because of their good stability, ready accessibility, and appealing structure-property relationship.6Yam V.W.-W. Au V.K.-M. Leung S.Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes.Chem. Rev. 2015; 115: 7589-7728Crossref PubMed Scopus (1064) Google Scholar, 7Gimeno M.C. Laguna A. Chalcogenide centred gold complexes.Chem. Soc. Rev. 2008; 37: 1952-1966Crossref PubMed Scopus (103) Google Scholar, 8Yam V.W.-W. Cheng E.C.-C. Highlights on the recent advances in gold chemistry—a photophysical perspective.Chem. Soc. Rev. 2008; 37: 1806-1813Crossref PubMed Scopus (452) Google Scholar Similar to the metallic nanoclusters and quantum dots,9Fernando A. Weerawardene K.L. Karimova N.V. Aikens C.M. Quantum mechanical studies of large metal, metal oxide, and metal chalcogenide nanoparticles and clusters.Chem. Rev. 2015; 115: 6112-6216Crossref PubMed Scopus (286) Google Scholar, 10Santiago-Gonzalez B. Monguzzi A. Azpiroz J.M. Prato M. Erratico S. Campione M. Lorenzi R. Pedrini J. Santambrogio C. Torrente Y. et al.Permanent excimer superstructures by supramolecular networking of metal quantum clusters.Science. 2016; 353: 571-575Crossref PubMed Scopus (38) Google Scholar, 11Nozik A.J. Beard M.C. Luther J.M. Law M. Ellingson R.J. Johnson J.C. Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells.Chem. Rev. 2010; 110: 6873-6890Crossref PubMed Scopus (1064) Google Scholar, 12Zeng C. Chen Y. Kirschbaum K. Lambright K.J. Jin R. Emergence of hierarchical structural complexities in nanoparticles and their assembly.Science. 2016; 354: 1580-1584Crossref PubMed Scopus (385) Google Scholar diverse cluster configurations and attractive structure-dependent photophysics have also been discovered for the gold(I)-chalcogenido and phosphinidene clusters,6Yam V.W.-W. Au V.K.-M. Leung S.Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes.Chem. Rev. 2015; 115: 7589-7728Crossref PubMed Scopus (1064) Google Scholar, 7Gimeno M.C. Laguna A. Chalcogenide centred gold complexes.Chem. Soc. Rev. 2008; 37: 1952-1966Crossref PubMed Scopus (103) Google Scholar, 8Yam V.W.-W. Cheng E.C.-C. Highlights on the recent advances in gold chemistry—a photophysical perspective.Chem. Soc. Rev. 2008; 37: 1806-1813Crossref PubMed Scopus (452) Google Scholar, 13Lee T.K.-M. Zhu N. Yam V.W.-W. An Unprecedented luminescent polynuclear gold(I) μ3-sulfido cluster with a thiacrown-like architecture.J. Am. Chem. Soc. 2010; 132: 17646-17648Crossref PubMed Scopus (100) Google Scholar, 14Yao L.Y. Yam V.W.-W. Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.J. Am. Chem. Soc. 2015; 137: 3506-3509Crossref PubMed Scopus (44) Google Scholar, 15Yao L.Y. Hau F.K.-W. Yam V.W.-W. Addition reaction-induced cluster-to-cluster transformation: controlled self-assembly of luminescent polynuclear gold(I) μ3-sulfido clusters.J. Am. Chem. Soc. 2014; 136: 10801-10806Crossref PubMed Scopus (50) Google Scholar, 16Pei X.L. Yang Y. Lei Z. Chang S.S. Guan Z.J. Wan X.K. Wen T.B. Wang Q.M. Highly active gold(I) silver(I) oxo cluster activating sp3 C-H bonds of methyl ketones under mild conditions.J. Am. Chem. Soc. 2015; 137: 5520-5525Crossref PubMed Scopus (37) Google Scholar, 17Hau F.K.-W. Lee T.K.-M. Cheng E.C.-C. Au V.K.-M. Yam V.W.-W. Luminescence color switching of supramolecular assemblies of discrete molecular decanuclear gold(I) sulfido complexes.Proc. Natl. Acad. Sci. USA. 2014; 111: 15900-15905Crossref PubMed Scopus (54) Google Scholar, 18Yao L.-Y. Lee T.K.-M. Yam V.W.-W. Thermodynamic-driven self-assembly: heterochiral self-sorting and structural reconfiguration in gold(I)-sulfido cluster system.J. Am. Chem. Soc. 2016; 138: 7260-7263Crossref PubMed Scopus (55) Google Scholar, 19Lee T.K.-M. Cheng E.C.-C. Zhu N. Yam V.W.-W. Hexanuclear gold(I) phosphide complexes as platforms for multiple redox-active ferrocenyl units.Chemistry. 2014; 20: 304-310Crossref PubMed Scopus (9) Google Scholar, 20Cheng E.C.-C. Lo W.Y. Lee T.K.-M. Zhu N. Yam V.W.-W. Synthesis, characterization, and luminescence studies of discrete polynuclear gold(I) sulfido and selenido complexes with intramolecular aurophilic contacts.Inorg. Chem. 2014; 53: 3854-3863Crossref PubMed Scopus (38) Google Scholar which endowed them with promising applications in luminescence,6Yam V.W.-W. Au V.K.-M. Leung S.Y.-L. Light-emitting self-assembled materials based on d8 and d10 transition metal complexes.Chem. Rev. 2015; 115: 7589-7728Crossref PubMed Scopus (1064) Google Scholar chemosensing,13Lee T.K.-M. Zhu N. Yam V.W.-W. An Unprecedented luminescent polynuclear gold(I) μ3-sulfido cluster with a thiacrown-like architecture.J. Am. Chem. Soc. 2010; 132: 17646-17648Crossref PubMed Scopus (100) Google Scholar structural transformaion,14Yao L.Y. Yam V.W.-W. Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.J. Am. Chem. Soc. 2015; 137: 3506-3509Crossref PubMed Scopus (44) Google Scholar, 15Yao L.Y. Hau F.K.-W. Yam V.W.-W. Addition reaction-induced cluster-to-cluster transformation: controlled self-assembly of luminescent polynuclear gold(I) μ3-sulfido clusters.J. Am. Chem. Soc. 2014; 136: 10801-10806Crossref PubMed Scopus (50) Google Scholar catalysis,16Pei X.L. Yang Y. Lei Z. Chang S.S. Guan Z.J. Wan X.K. Wen T.B. Wang Q.M. Highly active gold(I) silver(I) oxo cluster activating sp3 C-H bonds of methyl ketones under mild conditions.J. Am. Chem. Soc. 2015; 137: 5520-5525Crossref PubMed Scopus (37) Google Scholar nanoaggregates,17Hau F.K.-W. Lee T.K.-M. Cheng E.C.-C. Au V.K.-M. Yam V.W.-W. Luminescence color switching of supramolecular assemblies of discrete molecular decanuclear gold(I) sulfido complexes.Proc. Natl. Acad. Sci. USA. 2014; 111: 15900-15905Crossref PubMed Scopus (54) Google Scholar chiral self-sorting,18Yao L.-Y. Lee T.K.-M. Yam V.W.-W. Thermodynamic-driven self-assembly: heterochiral self-sorting and structural reconfiguration in gold(I)-sulfido cluster system.J. Am. Chem. Soc. 2016; 138: 7260-7263Crossref PubMed Scopus (55) Google Scholar and so on. Inspired by nature, bottom-up construction of ordered, sophisticated, and functional supramolecular structures and materials through a self-assembly approach has emerged to be among one of the most important topics in the science community in the past few decades.21Lehn J.M. Supramolecular chemistry - scope and perspectives molecules, supermolecules, and molecular devices.Angew. Chem. Int. Ed. 1988; 27: 89-112Crossref Scopus (3279) Google Scholar, 22Chakrabarty R. Mukherjee P.S. Stang P.J. Supramolecular coordination: self-assembly of finite two- and three-dimensional ensembles.Chem. Rev. 2011; 111: 6810-6918Crossref PubMed Scopus (2289) Google Scholar, 23Fujita M. Metal-directed self-assembly of two- and three-dimensional synthetic receptors.Chem. Soc. Rev. 1998; 27: 417-425Crossref Scopus (1347) Google Scholar, 24Avci C. Imaz I. Carné-Sánchez A. Pariente J.A. Tasios N. Pérez-Carvajal J. Alonso M.I. Blanco A. Dijkstra M. López C. et al.Self-assembly of polyhedral metal-organic framework particles into three-dimensional ordered superstructures.Nat. Chem. 2017; 10: 78-84Crossref PubMed Google Scholar, 25Wu Y.L. Horwitz N.E. Chen K.S. Gomez-Gualdron D.A. Luu N.S. Ma L. Wang T.C. Hersam M.C. Hupp J.T. Farha O.K. et al.G-quadruplex organic frameworks.Nat. Chem. 2017; 9: 466-472Crossref PubMed Scopus (79) Google Scholar, 26Lei Z. Pei X.-L. Jiang Z.-G. Wang Q.-M. Cluster linker approach: preparation of a luminescent porous framework with NbO topology by linking silver ions with gold(I) clusters.Angew. Chem. Int. Ed. 2014; 53: 12771-12775Crossref PubMed Scopus (89) Google Scholar, 27Howarth A.J. Liu Y. Li P. Li Z. Wang T.C. Hupp J.T. Farha O.K. Chemical, thermal and mechanical stabilities of metal-organic frameworks.Nat. Rev. Mater. 2016; 1: 15018Crossref Scopus (1150) Google Scholar, 28Hudson Z.M. Boott C.E. Robinson M.E. Rupar P.A. Winnik M.A. Manners I. Tailored hierarchical micelle architectures using living crystallization-driven self-assembly in two dimensions.Nat. Chem. 2014; 6: 893-898Crossref PubMed Scopus (271) Google Scholar, 29Li P. Vermeulen N.A. Malliakas C.D. Gómez-Gualdrón D.A. Howarth A.J. Mehdi B.L. Dohnalkova A. Browning N.D. O'Keeffe M. Farha O.K. Bottom-up construction of a superstructure in a porous uranium-organic crystal.Science. 2017; 356: 624-627Crossref PubMed Scopus (230) Google Scholar, 30Yamagishi H. Fukino T. Hashizume D. Mori T. Inoue Y. Hikima T. Takata M. Aida T. Metal-organic nanotube with helical and propeller-chiral motifs composed of a C-10-symmetric double-decker nanoring.J. Am. Chem. Soc. 2015; 137: 7628-7631Crossref PubMed Scopus (38) Google Scholar To achieve hierarchical self-assembly in artificial systems as accurate, complex, and functional as that in biosystems has always been one of the biggest challenges for the chemists in this field. The feasible post-modification, modulatable cluster configuration, structure-dependent photophysics, and nanosized zero-dimensional structure of polynuclear gold(I)-chalcogenido clusters have made them fascinating candidates for bottom-up construction of novel luminescent materials.14Yao L.Y. Yam V.W.-W. Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.J. Am. Chem. Soc. 2015; 137: 3506-3509Crossref PubMed Scopus (44) Google Scholar, 15Yao L.Y. Hau F.K.-W. Yam V.W.-W. Addition reaction-induced cluster-to-cluster transformation: controlled self-assembly of luminescent polynuclear gold(I) μ3-sulfido clusters.J. Am. Chem. Soc. 2014; 136: 10801-10806Crossref PubMed Scopus (50) Google Scholar, 26Lei Z. Pei X.-L. Jiang Z.-G. Wang Q.-M. Cluster linker approach: preparation of a luminescent porous framework with NbO topology by linking silver ions with gold(I) clusters.Angew. Chem. Int. Ed. 2014; 53: 12771-12775Crossref PubMed Scopus (89) Google Scholar, 31Fenske D. Langetepe T. Kappes M.M. Hampe O. Weis P. Selenium-bridged gold(I) complex cations[Au10Se4(dppm)4]2+ and [Au18Se8(dppe)6]2+.Angew. Chem. Int. Ed. 2000; 39: 1857-1860Crossref PubMed Scopus (72) Google Scholar, 32Perry J.J. Perman J.A. Zaworotko M.J. Design and synthesis of metal-organic frameworks using metal-organic polyhedra as supermolecular building blocks.Chem. Soc. Rev. 2009; 38: 1400-1417Crossref PubMed Scopus (1610) Google Scholar Nevertheless, the exploration of polynuclear gold(I)-chalcogenido clusters has mainly been confined to the study of their structure and bonding as well as molecular characteristics; more efforts on their functional properties are imperative for the development of their material features and applications. In nature, biomolecules of high structural order, such as DNA and proteins, are hierarchically constructed via hydrogen bonding with certain rotational direction or handedness in general.33Parkinson G.N. Lee M.P.H. Neidle S. Crystal structure of parallel quadruplexes from human telomeric DNA.Nature. 2002; 417: 876-880Crossref PubMed Scopus (1692) Google Scholar, 34He Y. Ye T. Su M. Zhang C. Ribbe A.E. Jiang W. Mao C. Hierarchical self-assembly of DNA into symmetric supramolecular polyhedra.Nature. 2008; 452: 198-201Crossref PubMed Scopus (1006) Google Scholar, 35Engelhard D.M. Nowack J. Clever G.H. Copper-induced topology switching and thrombin inhibition with telomeric DNA G-quadruplexes.Angew. Chem. Int. Ed. 2017; 56: 11640-11644Crossref PubMed Scopus (43) Google Scholar, 36Witte K. Skolnick J. Wong C.H. A synthetic retrotransition (backward reading) sequence of the right-handed three-helix bundle domain (10–53) of protein A shows similarity in conformation as predicted by computation.J. Am. Chem. Soc. 1998; 120: 13042-13045Crossref Scopus (11) Google Scholar Artificial systems of relevance to chiral structure and hierarchical self-assembly should be important for the understanding and the mimicking of biological processes.30Yamagishi H. Fukino T. Hashizume D. Mori T. Inoue Y. Hikima T. Takata M. Aida T. Metal-organic nanotube with helical and propeller-chiral motifs composed of a C-10-symmetric double-decker nanoring.J. Am. Chem. Soc. 2015; 137: 7628-7631Crossref PubMed Scopus (38) Google Scholar, 37Liu M. Zhang L. Wang T. Supramolecular chirality in self-assembled systems.Chem. Rev. 2015; 115: 7304-7397Crossref PubMed Scopus (1240) Google Scholar, 38Scarso A. Rebek Jr., J.J. Chiral spaces in supramolecular assemblies.Top. Curr. Chem. 2006; 265: 1-46Crossref Scopus (55) Google Scholar, 39Ziegler M. Davis A.V. Johnson D.W. Raymond K.N. Supramolecular chirality: a reporter of structural memory.Angew. Chem. Int. Ed. 2003; 42: 665-668Crossref PubMed Scopus (130) Google Scholar However, achieving the precise control of multilevel hierarchy and chirality of artificial systems still presents a major challenge.38Scarso A. Rebek Jr., J.J. Chiral spaces in supramolecular assemblies.Top. Curr. Chem. 2006; 265: 1-46Crossref Scopus (55) Google Scholar There is a need for an in-depth understanding of the higher hierarchical structure and origin of chirality and their associated mechanism in nature. Herein, we report a C4-symmetric structure-based25Wu Y.L. Horwitz N.E. Chen K.S. Gomez-Gualdron D.A. Luu N.S. Ma L. Wang T.C. Hersam M.C. Hupp J.T. Farha O.K. et al.G-quadruplex organic frameworks.Nat. Chem. 2017; 9: 466-472Crossref PubMed Scopus (79) Google Scholar, 33Parkinson G.N. Lee M.P.H. Neidle S. Crystal structure of parallel quadruplexes from human telomeric DNA.Nature. 2002; 417: 876-880Crossref PubMed Scopus (1692) Google Scholar, 35Engelhard D.M. Nowack J. Clever G.H. Copper-induced topology switching and thrombin inhibition with telomeric DNA G-quadruplexes.Angew. Chem. Int. Ed. 2017; 56: 11640-11644Crossref PubMed Scopus (43) Google Scholar chiral gold quartet framework (GQF) (Figure 1A) assembled from four decanuclear gold(I) μ3-sulfido clusters ([Au10(dpptrz)4S4]2−, dpptrz-Au10), which were obtained by click-reaction-induced cluster-to-cluster transformation (CCT) from an octadecanuclear gold(I) μ3-sulfido cluster ([(dppa)6Au18S8]2+, dppa-Au18). A combination of bottom-up construction, hierarchy, and spontaneous symmetry breaking involving aurophilic interactions, hydrogen bonding, and Na-X (X = N and O) coordination was found in the self-assembly (Figure 1B). The unique GQF showed a body-centered tetragonal (bct) close packing of the chiral I4 space group in a single crystal (Figure 1B). Reversible anisotropic structural transformation accompanied by luminescence changes were observed for the GQF in a single-crystal-to-single-crystal (SCSC) manner (Figure 1C). The present work provides an alternative motif and important insights for the development of artificial hierarchical systems and stimuli-responsive luminescent materials based on versatile polynuclear gold(I)-sulfido-cluster building blocks. By bubbling H2S into a white suspension of [(dppa)(AuCl)2] in a mixed solvent of dichloromethane-methanol-pyridine, we obtained and characterized dppa-Au18 (see “Synthesis and Characterization” in the Supplemental Information; Figure S6). Single-crystal X-ray diffraction (SCXRD) analysis revealed a Au18-sulfido cluster, [(dppa)6Au18S8]2+ (see “X-Ray Crystallography” in the Supplemental Information; Figures 2A and S7), analogous to the structure of the previously reported trans-dppee-ligated Au18 cluster.14Yao L.Y. Yam V.W.-W. Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.J. Am. Chem. Soc. 2015; 137: 3506-3509Crossref PubMed Scopus (44) Google Scholar The observation of a singlet at ca. δ = 17.73 ppm in the 31P{1H} NMR spectrum of dppa-Au18 in CDCl3 indicates the possible presence of a D3d symmetry in this solvent medium. Nevertheless, two singlets at δ 17.12 and 17.77 ppm were observed for this dppa-Au18 in DMSO-d6 (Figure S8), indicating the existence of symmetry reduction from D3d to D3 in a different solvent medium. Reacting dppa-Au18 with sodium azide in DMSO led to an efficient and complete click reaction with heating at around 110°C to give a totally new click product complex, dpptrz-Au10 (Figure 2A). Monitoring of the 31P{1H} NMR spectral changes during the click reaction of dppa-Au18 with NaN3 showed the disappearance of the signals corresponding to dppa-Au18 and the growth of a pair of doublets at δ 7.55 and 7.97 ppm (Figure 2B), corresponding to the formation of the product. Based on our previous works,14Yao L.Y. Yam V.W.-W. Photoinduced isomerization-driven structural transformation between decanuclear and octadecanuclear gold(I) sulfido clusters.J. Am. Chem. Soc. 2015; 137: 3506-3509Crossref PubMed Scopus (44) Google Scholar, 17Hau F.K.-W. Lee T.K.-M. Cheng E.C.-C. Au V.K.-M. Yam V.W.-W. Luminescence color switching of supramolecular assemblies of discrete molecular decanuclear gold(I) sulfido complexes.Proc. Natl. Acad. Sci. USA. 2014; 111: 15900-15905Crossref PubMed Scopus (54) Google Scholar, 40Yam V.W.-W. Cheng E.C.-C. Zhou Z.-Y. A highly soluble luminescent decanuclear gold(I) complex with a propeller-shaped structure.Angew. Chem. Int. Ed. 2000; 39: 1683-1685Crossref PubMed Scopus (137) Google Scholar the pair of doublets could be unambiguously assigned to the formation of a decanuclear (Au10) gold(I)-sulfido cluster with S4 molecular symmetry. In high-resolution electrospray ionization mass spectra (Figures S9–S13), the negatively charged cluster ion observed at about m/z = 1,921.51 ([M]2−) corresponds to the chemical formula of this newly formed cluster with [Au10(dpptrz)4S4]2− (dpptrz-Au10) (Figure S10). We also employed UV-visible (UV-vis) absorption spectroscopy to monitor the CCT process. During the course of the reaction, the absorption shoulder and maxima in the range of 355–550 nm (corresponding to dppa-Au18, Figure S14) decreased dramatically, and the increase in the absorption maximum at around 337 nm represents an unambiguous indication of the formation of the dpptrz-Au10 cluster (Figures 2C and S14). These results provide important insights and the possible mechanism for the click-reaction-triggered CCT process. The outer dppa ligands of dppa-Au18 would undergo click reaction with NaN3 to give a new type of diphosphine ligand dpptrz with totally different P−P bite distances and coordinating directions. As the click reaction proceeds, the formation of dpptrz ligands in the system would destroy the original Au(I)⋅⋅⋅Au(I) interactions as well as the Au18 cluster structures. The newly formed Au(I)⋅⋅⋅Au(I) interactions along with re-assembly of the Au units to give the Au10 clusters in the system finally direct and realize the click-reaction-triggered CCT from Au18 to Au10 (Figure 2A). To our knowledge, it is the first case of a click-reaction-induced CCT in gold(I)-sulfido cluster system, which should provide an important and efficient alternative in the construction of novel metal clusters through a post-synthetic approach. To further figure out the exact solid-state structure of this newly formed Au10 cluster (dpptrz-Au10), we attempted to isolate the cluster from the DMSO solution to obtain its SCXRD data. Yellow block crystals (dpptrz-Au10) with orange emission under UV light (365 nm) were obtained (Figure S15). Surprisingly, a complicated and sophisticated hierarchical framework structure was revealed by the SCXRD. A tetragonal chiral I4 space group was determined for this crystal. The observation of a triazole-based diphosphine-ligated Au10 cluster further confirms the success of the click-reaction-triggered CCT strategy (Figure S16). Since this cluster is dianionic, Na+ counter-cations were found in the crystal-packing lattice to balance the charge. Interestingly, a higher-level gold(I)-sulfido-cluster-based framework composed of sodium-oxo or -aqua clusters41Baier M. Bissinger P. Blümel J. Schmidbaur H. The intriguing structural characteristics of the heterosiloxane molecule Na4[Sb2O(OSiMe3)8].Chem. Ber. 1993; 126: 947-950Crossref Scopus (25) Google Scholar, 42Yi X.Y. Liu B. Jiménez-Aparicio R. Urbanos F.A. Gao S. Xu W. Chen J.S. Song Y. Zheng L.M. Syntheses, structures, and magnetic properties of mixed-valent diruthenium(II,III) diphosphonates with discrete and one-dimensional structures.Inorg. Chem. 2005; 44: 4309-4314Crossref PubMed Scopus (52) Google Scholar and dpptrz-Au10 was found in the crystals (Figure 3A). Zooming in on one single dpptrz-Au10 cluster reveals a pseudo-tetrahedral molecular geometry with the [Au10S4] core in the center and four dpptrz ligands (triazole rings) occupying the four corners of the tetrahedron (Figures 1A and 3A). In the solid state, four dpptrz-Au10 clusters tend to form an array in a face-to-face manner to give a C4-helical gold quartet with directional rotation, guided by inter-cluster hydrogen bonding and Na−O coordination41Baier M. Bissinger P. Blümel J. Schmidbaur H. The intriguing structural characteristics of the heterosiloxane molecule Na4[Sb2O(OSiMe3)8].Chem. Ber. 1993; 126: 947-950Crossref Scopus (25) Google Scholar, 42Yi X.Y. Liu B. Jiménez-Aparicio R. Urbanos F.A. Gao S. Xu W. Chen J.S. Song Y. Zheng L.M. Syntheses, structures, and magnetic properties of mixed-valent diruthenium(II,III) diphosphonates with discrete and one-dimensional structures.Inorg. Chem. 2005; 44: 4309-4314Crossref PubMed Scopus (52) Google Scholar, 43Zhang L. Xiang L. Hang C. Liu W. Huang W. Pan Y. From discrete molecular cages to a network of cages exhibiting enhanced CO2 adsorption capacity.Angew. Chem. Int. Ed. 2017; 56: 7787-7791Crossref PubMed Scopus (54) Google Scholar (Figure 3). The distances of the short inter-cluster C−H⋅⋅⋅S hydrogen bonds (2.62 Å; Table S6) are comparable to that of similar interactions within proteins.44Ma C. Zhang Q. Zhang R. Wang D. Self-assembly of dialkyltin moieties and mercaptobenzoic acid into macrocyclic complexes with hydrophobic “pseudo-cage” or double-cavity structures: supramolecular infrastructures involving intermolecular C–H⋅⋅⋅S weak hydrogen bonds and π- π interactions.Chem. Eur. J. 2005; 12: 420-428Crossref PubMed Scopus (84) Google Scholar, 45Zhou P. Tian F. Lv F. Shang Z. Geometric characteristics of hydrogen bonds involving sulfur atoms in proteins.Proteins. 2009; 76: 151-163Crossref PubMed Scopus (187) Google Scholar, 46Adman E. Watenpaugh K.D. Jensen L.H. NH⋅⋅⋅S hydrogen-bonds in Peptococcus aerogenes ferredoxin, Clostridium pasteurianum rubredoxin, and Chromatium high potential iron protein.Proc. Natl. Acad. Sci. USA. 1975; 72: 4854-4858Crossref PubMed Scopus (323) Google Scholar The outermost protecting phenyl rings are also highly ordered with rotational direction (Figures 3B and 3C). Overall, it presents a chiral C4-helical quartet structure. Furthermore, every two gold quartets are linked by the cubic sodium-oxo clusters at the pole to give 1D polymer packing along the c axis (Figures 3D and 3E). The waists of the gold quartets are further linked by sodium-aqua clusters as well as inter-cluster C−H⋅⋅⋅N hydrogen bonds (Table S6) to extend along the ab plane to give a 3D quartet framework in the solid state (Figures 3F and 3G). Finally, a bct close packing of tetragonal chiral I4 space group is represented for the GQF. It should be of interest to have spontaneous symmetry breaking to result in chiral assemblies from nonchiral species, not to mention the supramolecular self-assembly to give the hierarchical chiral superstructure in this w