Crystal structure of catena-poly[[[dichloridocopper(II)]-{μ-tert-butyl N-methyl-N-[4-(6-{[4-(pyridin-2-yl-κN)-1H-1,2,3-triazol-1-yl-κN 3]methyl}-1,3-benzothiazol-2-yl)phenyl]carbamato}] acetonitrile monosolvate]

The title coordination polymer was obtained by combining an aqueous solution of copper(II) dichloride with the ligand {tert-butylmethyl[4-(6-{[4-(pyridin-2-yl-)1H-1,2,3-triazol-1-yl]methyl}-1,3-benzothiazol-2-yl)phenyl]carbamate in acetonitrile.


Chemical context
Alzheimer's Disease (AD) is a neurodegenerative disease characterized by aggregation of amyloid peptide and extensive inflammation related to a strong oxidative stress (Cheignon et al., 2018). Metals are known to play a key role in this oxidative stress and also to be associated with peptide aggregation, at the core of the pathology (Faller et al., 2013;Viles, 2012). More specifically, Cu II has been found to form a complex with the amyloid peptide for which aggregation is one of the major hallmarks of AD (Eury et al., 2011;Faller et al., 2014). This has triggered significant ongoing interest in the development of chelators able to interact with metals in the context of AD (Santos et al., 2016;Conte-Daban et al., 2017).
In the course of our studies on the development of bifunctional molecules able to target amyloid fibrils, for example via a 2-arylbenzothiazole core (Noel et al., 2013), and interact with copper ions found within the senile plaques, we have designed and synthesized a benzothiazole moiety decorated with a triazole-pyridine subunit, viz. tert-butyl methyl [4-(6-{[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]methyl} benzo[d]thiazol-2-yl]phenyl}carbamate (L). Indeed integrating the N-binding from the triazole moiety in the binding site of a chelator has been shown to be a successful approach (Jones et al., 2012(Jones et al., , 2017. Compared to these seminal works, the additional aryl-benzothiazole moiety in compound L is expected to enhance the ability of the chelator to interact with amyloid aggregates and thus to retrieve deleterious Cu II ions ISSN 2056-9890 from A fibrils. Investigation of the ability to chelate Cu II ions, by studying the reaction of L with CuCl 2 , led to the formation of the title coordination polymer whose synthesis and molecular and crystal structures are described herein.

Figure 2
A view along the a axis of the acetonitrile solvent molecules (ball and stick) linked to the polymer chains, that propagate along direction [111], via a C-HÁ Á ÁN hydrogen bond (see Table 2 for details). Other H atoms have been omitted for clarity.

Figure 1
The molecular structure of the asymmetric unit of the title coordination polymer, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level. The H atoms have been omitted for clarity.

Figure 4
A view along the a axis of the crystal packing of the title compound, showing the hydrogen bonds as dashed lines (see Table 2 for details). H atoms not involved in these interactions have been omitted.

Synthesis and crystallization
The synthesis of the ligand, tert-butyl methyl[4-(6-{[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]methyl}benzo[d]thiazol-2-yl)phenyl]carbamate (L), was performed according to literature precedents (Noel et al., 2013;Jones et al., 2012). A mixture of 15 mg of L dissolved in 1 ml of acetonitrile, and 1.1 equiv. of CuCl 2 dissolved in 10 ml of a mixture acetonitrile/H 2 O (6/3) was heated to 353 K. The mixture was cooled at room temperature, allowing a precipitate to form. The supernatant was removed and the precipitate was dissolved with a minimum volume of hot acetonitrile, filtered and left at room temperature in a closed vessel producing overnight pale-green plate-like crystals.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The H atoms were all located in difference-Fourier maps, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry [C-H = 0.93-0.98 Å with U iso (H) = 1.5U eq (C-methyl) and 1.2U eq (C) for other H atoms], after which the positions were refined with riding constraints (Cooper et al., 2010).