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  • Title: Dipotassium and sodium/potassium crystalline picrate complexes with the crown ether 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]-[1,4, 7,10,13,16,19,22]octaoxacyclotetracosin (dibenzo-24-crown-8).
    Author: Gallagher T, Taylor MJ, Ernst SR, Hackert ML, Poonia NS.
    Journal: Acta Crystallogr B; 1991 Jun 01; 47 ( Pt 3)():362-8. PubMed ID: 1832870.
    Abstract:
    The crystal structures of the dipotassium and the mixed sodium/potassium picrate complexes with the crown ether dibenzo-24-crown-8 (DB24C8) were solved and found to be nearly identical. (I): NaK-pic2(DB24C8), [NaK(C6H2N3O7)2(C24H32O8)]. Mr = 966.8, triclinic, P1, a = 8.164 (2), b = 9.960 (2), c = 13.368 (3) A, alpha = 103.92 (3), beta = 108.03 (2), gamma = 93.23 (2) degrees, V = 993.0 (7) A3, Z = 1, Dm = 1.54 (T = 298 K). Dx = 1.62 (1) g cm-3, lambda = (Mo K alpha) 0.71069 A, mu = 2.37 cm-1, F(000) = 500, T = 103 K, R = 0.086 for 2904 unique reflections. (II): K2pic2(DB24C8), [K2(C6H2N3O7)2(C24H32O8)]. Mr = 982.9, triclinic, P1, a = 8.231 (4), b = 9.850 (2), c = 13.346 (4) A, alpha = 103.91 (2), beta = 106.82 (3), gamma = 93.37 (2) degrees, V = 995.7 (9) A3, Z = 1, Dm = 1.59 (T = 298 K), Dx = 1.638 (8) g cm-3, lambda (Mo K alpha) = 0.71069 A, mu = 3.30 cm-1, F(000) = 508, T = 163 K, R = 0.042 for 4835 unique reflections. Both structures feature eight-coordinated cations between alternating layers of relatively flat crown ligands and paired picrates. In the mixed-metal system the two cations are disordered between two P1-related sites; these metal sites have a coordination environment only slightly different from that in the dipotassium structure. Na+ is able to occupy an environment similar to that of K+ under the conditions of these crystals, a situation not previously observed in the chemistry of crown ethers or macrocylic multidentates.
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