Compound 5 was selected for characterization using STM due to the presence of carboxylic groups on the DT-TTF backbone which are known to facilitate the formation of hydrogen-bonded selfassembled networks. The self-assembly of 5 was studied using STM at the heptanoic acid/graphite interface. 5 forms long-range ordered crystalline networks at the heptanoic acid /graphite interface with domains extending over 150 nm. Large scale STM images show wellordered bright features ordered in a pseudo hexagonal arrangement (Fig. and S21, ESI †). Smaller scale STM image presented in Fig. shows a well-ordered arrangement of bright features which can be assigned to the electron rich DT-TTF core of 5. Unit cell parameters extracted from graphite calibrated STM images are a = 1.9 ± 0.1 nm, b = 2.3 ± 0.1 nm, γ = 62° ± 1°, which suggests the existence of a distorted hexagonal network. A molecular model built using calibrated STM data is presented in Fig. . The molecular model reveals that 5 forms one-dimensional hydrogen bonded chains using two diagonally opposite carboxyl groups present on the DT-TTF backbone. The remaining two carboxyl groups are thus not engaged in hydrogen bonding with neighbouring DT-TTF molecules and most likely interact with partially adsorbed molecules of heptanoic acid which was used as a solvent. The molecular model also reveals substantial empty areas between the hydrogen bonded 1D arrays of 5. These areas are possibly filled with partially/transiently adsorbed heptanoic acid molecules which are mobile on the time scale of STM measurements. The observation of partial hydrogen bonding between the molecules of 5 is not completely surprising. It is well known that molecular materials, especially those forming porous networks do not always scale with the size of the building blocks. This is because increased pore sizes are thermodynamically disfavoured and go against the natural tendency of close packing. If the molecules of 5 were to form a 2D network based on hydrogen bonding using its all four carboxyl groups, the resultant cavities would be too big to be stable. Thus, the system must make a compromise between forming strong two-fold hydrogen bonds between the remaining carboxyl groups and close packing. Under the experimental conditions used, the latter seems to be the choice. Such scalability study has been previously reported for self-assembled networks of aromatic tricarboxylic acids. Considering that intermolecular H-bonds formed between carboxylic acid groups are highly directional, it is likely that 5 reaches a planar geometry to form such SAMNs, as supported by the molecular model shown in Fig. as well as in further calculations shown in Fig. ). This planarization is the result of van der Waals interactions between the HOPG surface and the DT-TTF core extended with the phenyl groups.