The synthesis of a new TADF emitter, DMAC-py-TRZ, is presented, together with an extensive computational analysis and experimental characterization. The chemical structure of DMAC-py-TRZ only marginally differs from that of the parent DMAC-TRZ compound. However, this minor change of the bridging moiety between the donor and acceptor has an enormous impact on the conformation and hence on the photophysics of the compound. Specifically, while DMAC-TRZ maintains the same orthogonal geometry in both the ground and the first excited singlet states, DMAC-py-TRZ assumes a bent geometry in the ground state, as highlighted by the large oscillator strength measured in solution for this dye. However, upon excitation to the S1 state, the system undergoes a large geometrical rearrangement to the orthogonal structure. This large relaxation is confirmed by the very large Stokes shift measured in non-polar solvents. In frozen 2-MeTHF glass at very dilute conditions, the relaxation is hindered and only a blue-shifted emission is seen from the unrelaxed bent conformer, without any hint of emission from the orthogonal structure. In mCP films a distribution of conformers exists and at low concentrations dual emission is observed, originating both from both the bent and orthogonal structures. However, upon increasing the doping concentration, the emission from the orthogonal conformer dominates. While self-absorption can be partly responsible for the phenomenon, we conclude that an efficient energy transfer from one conformer to the other also contributes to the spectral change. Indeed, TADF is not expected nor observed in the bent structure, due to a too large DEST. The good TADF efficiency of DMAC-py-TRZ in solution, similar as for DMAC-TRZ, is in line with the very fast molecular relaxation from the bent (TADF-silent) to the orthogonal geometry (TADFactive) in solution. The situation is more delicate in matrices where the host rigidity hinders a large molecular rearrangement. The observed good efficiency of TADF in matrices then suggests efficient energy transfer of excitons created on the bent (and TADF silent) structures towards molecules in the orthogonal (and TADF-active) structure as to retrieve all photogenerated singlet states for TADF activity. Most probably, efficient triplet-to-triplet energy transfer is also required to explain the good efficiency of DMACpy-TRZ OLEDs, but this will be subject of a subsequent study.