Polymorphism of [Cu₁₅(PhCH₂CH₂S)₁₃(PPh₃)₆][BF₄]₂ and Double-Helical Assembly of [Cu₁₈H(PhCH₂CH₂S)₁₄(PPh₃)₆Cl₃]: Origin of Two Chiral Nanoclusters with Triple-Helical Core from Intermediates

High Resolution Image Download MS PowerPoint Slide Here, we report the solvent-induced polymorphism in [Cu 15 (PET) 13 (TPP) 6 ][BF 4 ] 2 (Cu 15 ) (TPP = triphenylphosphine, PET = 2-phenylethanthiol), and double-helical assembly of the [Cu 18 H(PET) 14 (TPP) 6 Cl 3 ] (Cu 18 ) nanocluster (NC) from reaction intermediates. Both copper NCs have an intrinsically chiral triple-stranded helicate metal core, unlike traditional copper NCs with a polyhedral-based kernel. The chiral structure of Cu 15 resembles an enantiomeric pair in the unit cell. Moreover, Cu 18 has a three-layered 3D chirality of a sandwich constructed of sulfur-bridged copper NCs aligned in a top-middle-down configuration. Furthermore, the Cu 18 NC self-hierarchically assembles into a complex double-stranded helix secondary structure sustained by noncovalent interactions. Electrospray ionization mass spectrometry (ESI-MS), density functional theory (DFT), and X-ray photoelectron spectroscopy (XPS) were utilized to validate the single-crystal X-ray diffraction (SCXRD) data. Overall, this study provides an interesting example of polymorphism, chirality, and hierarchical double-helical assembly of NCs, allowing for extensive understanding of complicated structures at the atomic level.