Coordination polymers of increasing complexity derived from alkali metal cations and (4-Amino-1-hydroxybutylidine)-1,1-bisphosphonic acid (alendronic acid): the competitive influences of coordination and supramolecular interactions

Deacon, Glen B., Forsyth, Craig M., Greenhill, Neil B., Junk, Peter C., and Wang, Jun (2015) Coordination polymers of increasing complexity derived from alkali metal cations and (4-Amino-1-hydroxybutylidine)-1,1-bisphosphonic acid (alendronic acid): the competitive influences of coordination and supramolecular interactions. Crystal Growth and Design, 15 (9). pp. 4646-4662.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website: http://dx.doi.org/10.1021/acs.cgd.5b0091...
 
4
1


Abstract

Reactions of alendronic acid (= LH5) with group 1 metal bases KOH, KHCO3, Rb2CO3, RbOH, or Cs2CO3 gave the corresponding complexes [M(LH4)(H2O)n]·m(H2O), M = K, Rb, or Cs. Crystallization of the products under varying conditions yielded differing hydrates and/or polymorphic phases. Reactions of (4-amino-1-hydroxybutylidine)-1,1-bisphosphonic acid (alendronic acid = LH5) with 1 equiv of the group 1 metal bases KOH, KHCO3, Rb2CO3, RbOH, or Cs2CO3 in aqueous solution at pH 4–5 gave the corresponding complexes [M(LH4)(H2O)n]·m(H2O), M = K (1), Rb (2), or Cs (3). Crystallization of the products under varying conditions yielded differing hydrates and/or polymorphic phases. Rapid crystallization of the potassium complex 1 from water/EtOH or water/DMSO gave 2[K(LH4)]·3(H2O) (1a), whereas slow crystallization from water or water/DMSO gave [K2(LH4)2(H2O)2]·2H2O (1b phase I). For the rubidium complex 2, rapid crystallization from water/EtOH gave the analogous [Rb2(LH4)2(H2O)2]·2H2O (2b phase I), whereas slow crystallization from water/DMSO also gave 2b, but as a mixture of phase I and the structural polymorph [Rb(LH4)(H2O)]·H2O (2b phase II). In contrast, only [Cs(LH4)(H2O)]·H2O (3b phase II) was obtained for the cesium complex 3 under all crystallization conditions. A second complex type [M(LH4)(LH5)]·2H2O (M = Rb 4, Cs 5), incorporating an additional coordinated alendronic acid molecule, was also observed for the larger metals Rb and Cs as a minor product in some syntheses and isolated by fractional crystallization for 4, but as the sole product from Cs(O2CH) and LH5 for 5. The crystal structures of the complexes [M(LH4)(H2O)n]·m(H2O) 1a, 2b (phase II), and 3b (phase II) comprise edge-shared or corner-shared polyhedral chains that are linked by bridging bisphosphonate ligands into two-dimensional (2-D) sheets. The 4-ammoniobutylidene chains protrude above and below the coordination layers and interact with neighboring layers through hydrogen bonding of the terminal ammonium group forming distinctive supramolecular three-dimensional (3-D) arrays. The phase I structure of 1b and 2b comprises ribbons of parallel M4(LH4)4(H2O)4 subunits arranged in a more close packed 3-D supramolecular network. For [M(LH4)(LH5)]·2H2O (M = Rb 4, Cs 5), isolated M+ cations, bridged by bisphosphonate ligands, are arranged into 2-D sheets, with the pendant 4-ammoniumbutylidene chains resulting in a 3-D lamellar network similar to those of 1a and 2b/3b (phase II). All of the [M(LH4)(H2O)n]·m(H2O) and [M(LH4)(LH5)]·2H2O structures display strong PO–H···O(phosphonate) and N–H···O(phosphonate/water) hydrogen bond motifs which significantly impact the observed structures. Reactions of LH5 with 2 equiv of the group 1 metal bases MOH (M = Na, K, Rb, Cs) at pH 9–10 gave the dimetalated complexes [M2(LH3)(H2O)n]·m(H2O) (M = Na 6, K 7, Rb 8, Cs 9). Crystallization of 6 from water/MeOH gave [Na2(LH3)(H2O)4]·H2O (6a) as a single phase. For 7, crystallization from water/MeOH gave K2(LH3)·3(H2O) (7a) as the bulk product, whereas crystals of [K2(LH3)(H2O)6] (7b) were grown from water/DMSO solutions. On standing, the crystals of 7b were converted into the bulk product 7a. The structures of 6a and 7b are chain rather than sheet bisphosphonate coordination polymers, with a high number of coordinated water molecules. Moreover, their 3-D supramolecular structures are distinguishable, viz. a pillared array for 6a and a more compact bilayer structure for 7b. The [M2(LH3)(H2O)n]·m(H2O) complexes of the larger group 1 metal cations 8 and 9 each crystallized as a mixture of phases. Crystals of [Rb2(LH3)(H2O)5]·(H2O) (8a) and [Cs4(LH3)2(H2O)9]·2(H2O) (9a), respectively, were identified as the major component after crystallization from DMSO/H2O. The lesser hydrates [Rb4(LH3)2(H2O)8]·(H2O) (8b) and [Cs2(LH3)(H2O)4] (9b) were also identified, but were not isolated as bulk materials. The structures of 8a, 8b, 9a, and 9b each were complex 2-D sheets of bisphosphonate metal coordination polymers, which assembled through supramolecular interactions into compact 3-D arrays.

Item ID: 41123
Item Type: Article (Refereed Research - C1)
ISSN: 1528-7505
Funders: Australian Research Council (ARC)
Projects and Grants: ARC Grant no. DP130100152
Date Deposited: 29 Oct 2015 01:01
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030204 Main Group Metal Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
Downloads: Total: 1
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page