Crystals of 3 of suitable quality for analysis using single X-ray crystal diffraction were obtained by slow evaporation of a saturated DMSO solution (CCDC 2101004). Compound 3 crystallises in the space group P21/n with one formula unit in the asymmetric unit and two DMSO solvents of crystallisation. Close intramolecular hydrogen bonds cause one of the urea groups to be positioned inwards to the centre of the molecule. This orientation allows for hydrogen bonding between the O3 urea carbonyl acceptor and the acridinone N4 donor group (N4•••O3: 2.736(4) Å), and between O3 and the phenyl C5 donor (C5•••O3: 2.867 (4) Å). This close hydrogen bonding is also observed for the urea carbonyl O5 (C25•••O5: 2.896 (4) Å). Close hydrogen bonds also exist for one DMSO molecule with the outwardly facing urea, forming a R½6 motif between N-H donor groups to the DMSO oxygen acceptor (N2•••O8 2.796(4) Å, N3•••O8 2.800(4) Å).