Selective Binding of Open Frameworks Assembled from Nickel(II) Macrocyclic Complexes with Organic and Inorganic Guests

Inclusion studies for metal-organic open-frameworks, [Ni(C_10}H₂₄N₄)(H₂O)₂]₃[BTC]₂·24H₂O (1) and [Ni(C₁₀H₂₆N₆)]₃ [BTC]₂·18H₂O(2) (BTC^3- = 1,3,5-benzenetricarboxylate) with various organic andinorganic guest molecules have been carried out. 1 is the previously reportedmolecular floral lace with 1-D channels, where positively charged macrocyclic layersand negatively charged BTC^3- layers are alternately packed by hydrogen bondinginteractions. 2 is assembled in this study from nickel(II) hexaazamacrocyclic complexcontaining methyl pendant arms and BTC^3-. The X-ray structure of 2 shows thatthe nickel(II) complex and BTC^3- form a 2-D coordination polymer. The XRPD patternsof 2 indicate that framework of 2 is slightly deformed upon removal of waterguest molecules but restored upon rebinding of water. The host solid 1 binds MeOHin toluene, and 1,3,5-trihydroxybenzene (THB) and 4-hydroxyacetophenone (HAP) in EtOH/toluene (v/v = 1/4) solutions. The binding constants (K_f) of 1 forMeOH, THB, and HAP are 66.4 M^-1, 259 M^-1, and 13.9 M^-1,respectively. In the range of high concentration of the guest, however, the host showsvarious binding curves depending upon the types of guest. It binds PhOH in toluene,showing a sigmoid curve. It also binds transition metal complexes such as[Cu(NH₃)₄](ClO₄)₂, [Cu(ethylenediamine)₂](ClO₄)₂,[Cu(histamine)₂](ClO₄)₂, and[Cu(N,N'-bis(3-aminopropyl)ethylenediamine)](ClO₄)₂ in MeCN, with K_f values of 645 M^-1, 9.52 M^-1, 37.2 M^-1, and 6.00 M^-1,respectively. The host solid 2 binds selectively PhOH over PhCl and PhBr, showing that hydrogen bonding interaction between the host and guest plays an important role in the selectivity.