5,6-Dioxo-1,10-phenanthrolin-1-ium trifluoromethanesulfonate

In the structure of the title salt, C12H7N2O2 +·CF3SO3 −, the cation participates in hydrogen bonding with the dione group of an adjacent cation as well as with the trifluoromethanesulfonate anion. In addition, there is an extensive network of C—H⋯O interactions between the cations and anions. There are two formula units per asymmetric unit. The crystal studied exhibits inversion twinning.

The structure consists of a mono-protonated phendione cation and a trifluoromethanesulfonate (CF 3 SO 3 -) anion. The C═O bond lengths in the phendione cation (1.208 (2), 1.209 (2) and the metrical parameters involving the phendione N atoms are comparable in value to those found in neutral 1,10-phenanthroline-5,6-dione.
The N-H protons participate in hydrogen bonds with adjoining phendione cations. In addition there is an extensive network of weak C-H···O interactions to both phendione O and trifluoromethanesulfonate O atoms.

Experimental
A flask containing 1,10-phenanthroline hydrate (1.00 g, 5.04 mmol) and potassium bromide (5.95 g, 50.0 mmol) was placed in an ice bath. Concentrated sulfuric acid (20 ml) was added in small portions, followed by drop wise addition of concentrated nitric acid (10 ml). The resulting solution was heated for 2 h at 80-85° C and cooled to room temperature. The solution was then poured into 400 ml water and neutralized with sodium bicarbonate, after which the phendione was extracted with dichloromethane, and recrystallized using a methanol-water mixture.
The title compound was synthesized in an atmosphere saturated with N 2 . To a solution of silver trifluoromethanesulfonate (0.079 g) in 10 ml CH 3 CN (acidified to pH 2 using concentrated triflic acid), was added a solution (10 ml) of CH 3 CN containing 0.065 g of phendione (acidified to pH 2 using triflic acid). The final yellowish solution was filtered and allowed to slowly evaporate yield reddish brown crystals of the title compound.

Refinement
H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with a C-H distance of 0.95 Å and U iso (H) = 1.2U eq (C

Special details
Experimental. The data were measured to a 2θ limit of 50 °, but the low completeness was caused by Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.