Diverse Self-Assembly from Predesigned Conformationally Flexible Pentanuclear Clusters Observed in a Ternary Copper(II)–Triazolate–Sulfoisophthalate System: Synthesis, Structure, and Magnetism

Self-assembly from the predesigned
CuII5 secondary building unit (SBU) in the ternary
CuII–triazolate–sulfoisophthalate system
generates three interesting magnetic samples: an open pillared-layer
framework with nanosized CuII30 metallamacrocycle-based
sublayer (1), a (3,6)-connected 2-fold interpenetrating
network consisting of alternating CuII5 and
CuII1 cores (2), and a (4,8)-connected
architecture constructed from centrosymmetric CuII7 clusters and four-branched 5-sulfoisophthalate (sip3–) connectors (3). These various structures significantly
result from the variable connectivity and the slight expansion of
the predetermined conformationally flexible CuII5 SBUs. Furthermore, these intriguing structural motifs in 1–3 essentially induce different magnetic phenomena.
A field-dependent metamagnetic transition from antiferromagnetic ordering
to weak ferromagnetism is observed in the frustrated CuII30-based sublayer of 1. The paramagnetic
CuII1 core in 2 virtually contributes
to an S = 1/2 spin ground state
due to the completely compensated magnetic moment in the 1,2,3-triazolate
(ta–)-bridged CuII5 cluster
containing ribbon. In contrast, strong antiferromagnetic interactions
in the locally centrosymmetric CuII7 cluster
lead to an overall S = 1/2 spin
ground state of 3. Thus, the SBU-derived self-assembly
strategy provides important hints for polymetallic cluster based high-dimensional
magnetic materials, which also brings a new vision for the design
and construction of novel functional materials.