Solid-state (55)Mn NMR spectroscopy of bis(μ-oxo)dimanganese(IV) [Mn(2)O(2)(salpn)(2)], a model for the oxygen evolving complex in photosystem II

We have examined the antiferromagneticly coupled bis(μ-oxo)dimanganese(IV) complex [Mn(2)O(2)(salpn)(2)] (1) with (55)Mn solid-state NMR at cryogenic temperatures and first-principle theory. The extracted values of the (55)Mn quadrupole coupling constant, C(Q), and its asymmetry parameter, η(Q), for 1 are 24.7 MHz and 0.43, respectively. Further, there was a large anisotropic contribution to the shielding of each Mn(4+), i.e. a Δσ of 3375 ppm. Utilizing broken symmetry density functional theory, the predicted values of the electric field gradient (EFG) or equivalently the C(Q) and η(Q) at ZORA, PBE QZ4P all electron level of theory are 23.4 MHz and 0.68, respectively, in good agreement with experimental observations.     

Aminoheterocycles as synthons for combinatorial Biginelli reactions

Chlorotrimethylsilane (TMSCl) has been utilized as an efficient promoter and water scavenger in the synthesis of diverse dihydropyrimidines via Biginelli type MCR-heterocyclization using aminoheterocycles. High yields and a simple workup of target compounds enable the facile generation of combinatorial libraries comprising more than 2,000 compounds of high structural and functional diversity. A representative set of 89 compounds is described.