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The 1 : 2 reaction of the imidazole‐based dithiolate (2) with GeCl₂ • dioxane in THF/TMEDA gives3, a TMEDA‐complexed dithiolene‐based germylene. Compound3is converted to monothiolate‐complexed (5) and N‐heterocyclic carbene‐complexed (7) germanium(II) dithiolene complexes via Lewis base ligand exchange. A bis‐dithiolene‐based germylene (8), involving a 3c–4e S‐Ge‐S bond, has also been synthesized through controlled hydrolysis of7. The bonding nature of3,5, and8was investigated by both experimental and theoretical methods.

 

Abstract Glycerol monolaurate (GML), a naturally occurring monoglyceride, is widely used commercially for its antimicrobial properties. Interestingly, several studies have shown that GML not only has antimicrobial properties but is also an anti-inflammatory agent. GML inhibits peripheral blood mononuclear cell proliferation and inhibits T cell receptor (TCR)-induced signaling events. In this study, we perform an extensive structure activity relationship analysis to investigate the structural components of GML necessary for its suppression of human T cell activation. Human T cells were treated with analogs of GML, differing in acyl chain length, head group, linkage of acyl chain, and number of laurate groups. Treated cells were then tested for changes in membrane dynamics, LAT clustering, calcium signaling, and cytokine production. We found that an acyl chain with 12–14 carbons, a polar head group, an ester linkage, and a single laurate group at any position are all necessary for GML to inhibit protein clustering, calcium signaling, and cytokine production. Removing the glycerol head group or replacing the ester linkage with a nitrogen prevented derivative-mediated inhibition of protein cluster formation and calcium signaling, while still inhibiting TCR-induced cytokine production. These findings expand our current understanding of the mechanisms of action of GML and the of GML needed to function as a novel immunosuppressant. 

While the 1 : 1 reaction of 3 with an N-heterocyclic carbene ({(Me)CN(i-Pr)} 2 C:) in THF resulted in ligand-substituted product 4, the corresponding 1 : 2 reaction (in the presence of H 2 O) gives the first structurally characterized germanium tris(dithiolene)dianion 5 as the major product and the “naked” dithiolene radical 6˙ as a minor by-product. The structure and bonding of 4 and 5 were probed by experimental and theoretical methods. Our study suggests that carbene-mediated partial hydrolysis may represent a new method to access tris(dithiolene) complexes of main-group elements.