Singly- and Triply-Linked Magnetic Porphyrin Lanthanide Arrays

The introduction of paramagnetic metal centers into a conjugated π-system is a promising approach towards engineering spintronic materials. Here, we report an investigation of two types of spin-bearing dysprosium(III) and gadolinium(III) porphyrin dimers: singly meso-meso-linked dimers with twisted conformations and planar edge-fused ,meso,-linked tapes. The rare-earth spin centers sit out of the plane of the porphyrin, so that the singly linked dimers are chiral, and their enantiomers can be resolved, whereas the edge-fused tape complexes can be separated into syn and anti stereoisomers. We compare the crystal structures, UV-vis-NIR absorption spectra, electrochemistry, EPR spectroscopy and magnetic behavior of these complexes. Low temperature SQUID magnetometry measurements reveal intramolecular antiferromagnetic exchange coupling between the GdIII centers in the edge-fused dimers (syn isomer: J = –51 ±2 MHz; anti isomer: J = –19 ±3 MHz), whereas no exchange coupling is detected in the singly-linked twisted complex. The phase memory times, Tm, are in the range 8–10 µs at 3 K, which is long enough to test quantum computational schemes using microwave pulses. The syn and anti Dy2 edge-fused tapes both exhibit single molecule magnetic hysteresis cycles at temperatures below 0.5 K with slow magnetization dynamics.