Solid-State Coordination Chemistry of the Cu/Triazolate/X System (X = F^-, Cl^-, Br^-, I^-, OH^-, and SO₄^2-)

Hydrothermal reactions of 1,2,4-triazole with the appropriate copper salt have provided eight structurally unique members of the Cu/triazolate/X system, with X = F^-, Cl^-, Br^-, I^-, OH^-, and SO₄^2-. The anionic components X of [Cu₃(trz)₄(H₂O)₃]F₂ (1) and [Cu₆(trz)₄Br]Cu₄Br₄(OH) (4) do not participate in the framework connectivity, acting as isolated charge-compensating counterions. In contrast, the anionic subunits X of [Cu^IICu^I(trz)Cl₂] (2), [Cu₆(trz)₄Br₂] (3), [Cu^IICu^I(trz)Br₂] (5), [Cu₃(trz)I₂] (6), [Cu₆^IICu₂^I(trz)₆(SO₄)₃(OH)₂(H₂O)] (8), and [Cu₄(trz)₃]OH·7.5H₂O (9·7.5H₂O) are intimately involved in the three-dimensional connectivities. The structure of [Cu^IICu^I(trz)₂][Cu₃^II₄] (7) is constructed from two independent substructures:  a three-dimensional cationic {Cu₂(trz)₂}_nⁿ⁺ component and {Cu₃I₄}_n^n- chains. Curiously, four of the structures are mixed-valence Cu^I/Cu^II materials:  2, 5, 7, and 8. The only Cu^II species is 1, while 3, 4, 6, and 9·7.5H₂O exhibit exclusively Cu^I sites. The magnetic properties of the Cu^II species 1 and of the mixed-valence materials 5, 7, 8, and the previously reported [Cu₃(trz)₃OH][Cu₂Br₄] have been studied. The temperature-dependent magnetic susceptibility of 1 conforms to a simple isotropic model above 13 K, while below this temperature, there is weak ferromagnetic ordering due to spin canting of the antiferromagnetically coupled trimer units. Compounds 5 and 7 exhibit magnetic properties consistent with a one-dimensional chain model. The magnetic data for 8 were fit over the temperature range 2−300 K using the molecular field approximation with J = 204 cm^-1, g = 2.25, and zJ‘ = −38 cm^-1. The magnetic properties of [Cu₃(trz)₃OH][Cu₂Br₄] are similar to those of 8, as anticipated from the presence of similar triangular {Cu₃(trz)₃(μ³-OH)}²⁺ building blocks. The Cu^I species 3, 4, 6, and 9 as well as the previously reported [Cu₅(trz)₃Cl₂] exhibit luminescence thermochromism. The spectra are characterized by broad emissions, long lifetimes, and significant Stokes' shifts, characteristic of phosphorescence.