For 10 points, name this metal that has symbol Cu.
In April 2012, it was discovered that large quantities of this element can be intercalated into bismuth selenide nanoribbons without disrupting the host lattice. Along with magnesium, this metal may catalyze the DielsAlder reaction and increase the amount of hetero product rather than the ene product. It's not ruthenium, but it can catalyze the Huisgen cycloaddition by forming a pi-complex with the alkyne, lowering the alkyne's pKa. The halide of this element can be a substitute in the place of an aromatic amine group through a diazonium salt in the Sandmeyer reaction. One compound with this element changes colors to brick red when in solution with reducing sugars. That compound is Benedict's solution, and Fehling's solution also contains it. Its most common oxidation state causes it to appear blue in solution. For 10 points, name this metal that has symbol Cu.
In April 2012, it was discovered that large quantities of this element can be intercalated into bismuth selenide nanoribbons without disrupting the host lattice.
copper [accept Cu before mention]