In organic spin cluster, high-spin modules (component spin, S'), which are assembles of alternating spin sites and strong fCU's (e.g. 1, 3-phenylenes), are linked with weak fCU's (e.g. 3,4'-biphenylene) to form the cluster.
The spin cluster design has the following attributes:
- efficient modular synthesis,
- very few defect-prone triarylmethyl sites, protected by the 4-biphenyl substituent
- improved average yield per site for unpaired electrons (97- 98%),
- exchange coupling constants (J/K) for the biphenyl unit can be determined using Heisenberg Hamiltonian models
Numerous high-spin polyradicals have been prepared based upon the organic spin cluster approach. A few examples are shown below.
- A. Rajca, J. Wongsriratanakul, S. Rajca, "High-Spin Organic Polyradicals as Spin Clusters: Ferromagnetic Spin Coupling through Biphenyl Unit in Polyarylmethyl Tri-, Penta-, Hepta-, and Hexadecaradicals", J. Am. Chem. Soc., 1997,
- A. Rajca, J. Wongsriratanakul, S. Rajca, R. Cerny, "Dendritic-Macrocyclic
Very-High-Spin Organic Polyradical with S = 10", Angew. Chem. Int. Ed.,
1998, 37, 1229.
- A. Rajca, J. Wongsriratanakul, S. Rajca, "Magnetic Ordering in an Organic Polymer", Science, 2001, 294, 1503.
- S. Rajca, A. Rajca, J. Wongsriratanakul, P. Butler, S. Choi, "Organic Spin Clusters. Dendritic-Macrocyclic Polyarylmethyl Polyradical with Very High-Spin of S = 10 and its Derivatives: Synthesis, Magnetic Studies, and Small Angle Neutron Scattering" J. Am. Chem. Soc., 2004, 126, 6972.
- A. Rajca, J. Wongsriratanakul, S. Rajca, "Organic Spin Clusters: Macrocyclic-Macrocyclic Polyarylmethyl Polyradicals with Very High-Spin S = 5 - 13" J. Am. Chem. Soc., 2004, 126, 6608.
- A. Rajca, J. Wongsriratanakula, S. Rajca, R. L. Cerny, "Organic Spin Clusters: Annelated Macrocyclic Polyarylmethyl Polyradicals and Polymer with Very High-Spin S = 6 - 18" Chem. Eur. J., 2004, 10, 3144, (VIP).