Structural features of silver(I) and copper(I) bis(thiophene-2-carbaldehyde-imine) trifluoromethanesulfonate complexes in the solid state and in solution: Crystal structures of [Ag[Th-2-Ch=N-(S)-CHMePh]2](O3SCF3) and [Cu{5-Me-Th-2CH=N-i-Pr}2](O3SCF3) and a 1H, 19F and 109Ag NMR study