Seven-coordinate anion complex with a tren-based urea: Binding discrepancy of hydrogen sulfate in solid and solution states

Structural characterization of a hydrogen sulfate complex with a tren-based urea suggests that the anion is coordinated with six NH center dot center dot center dot O bonds (d(N)center dot center dot center dot(O) = 2.857 (3) to 3.092 (3) angstrom) and one OH center dot center dot center dot O bond (d(O)center dot center dot center dot(O) = 2.57 (2) angstrom) from three receptors; however, in solution the anion is bound within the pseudo-cavity of one receptor.