It was anticipated that the strong symmetry-driven complementarity between the (dipPhO) 8 Pc and TPP macrocycles, clearly shown by the scXRD structure of the PNC of (dipPhO) 8 PcFe-N-FeTPP, would facilitate TPP incorporation into PNC structures via the formation of non-covalently bound heterodimers. Pleasingly, co-crystallisation of metal-free tetraphenylporphyrin (TPP) with (dipPhO) 8 PcCo successfully provided cubic crystals suitable for scXRD, which revealed that the PNC structure was indeed composed of cofacial heterodimers (Fig. ). Within the crystals, the (dipPhO) 8 PcCo molecules are arranged in the usual PNC structure with each TPP partner placed into the large voids. This structure is denoted as PNC[cH 2 O-Co/vTPP], based on previously developed nomenclature. The exquisite structural complementarity of (dipPhO) 8 PcCo with TPP (Fig. ) is confirmed by the close cofacial distance of ~3.48 Å between planes of the four pyrrolic nitrogens of each macrocycle and by the close interaction of 2.44 Å between the ortho-hydrogen of the phenyl group of TPP and the meso-nitrogen of (dipPhO) 8 PcCo. Interestingly, the adventitious H2O axial ligands on the Co 2+ cations of (dipPhO) 8 PcCo are forced into the cavities of the PNC by the presence of the TPP (Fig. ), which is in contrast to the normal location of simple axial ligands of the previously prepared PNCs from (dipPhO)8PcCo, in which they are placed in the void (e.g. PNC [Co-vPy] and PUNC[cC60/Co-vH2O]). Further co-crystallisations of TPP with metal-free (dipPhO) 8 PcH 2 or a range of metal-containing (dipPhO) 8 PcM complexes (M = Ti=O, Mn-Cl, Fe-Cl, Ni, Cu, Ag, and Au) all provided similar PNC structures within which there was full occupancy of the TTP molecule. Evidence that TPP encourages PNC formation is provided by successfully obtaining PNC[H 2 /vTPP], PNC[Ni/vTPP], PNC[Cu/vTPP] and PNC[Ag/vTPP], as without TPP each of these (dipPhO) 8 PcM components form only a non-porous crystal. A particularly satisfying result is the formation of PNC[Ni/vTPP] as (dipPhO) 8 PcNi has, to date, failed to provide a PNC either by itself or by co-crystallisation with C 60 , a strategy that had previously succeeded in obtaining PNCs from (dipPhO) 8 PcM with M = H 2 , Cu and Ag. Co-crystallisations of TPP and (dipPhO) 8 PcM (M = Al-OH, Ga-Cl and In-Cl) provided PNC structures with high but not full occupancy of TPP (estimated at >80%). Modelling of the scXRD data from crystals derived from (dipPhO) 8 PcZn and TPP indicated a 60% occupancy of the latter macrocycle within the PNC structure. However, all attempts failed to achieve cocrystals of TPP with (dipPhO) 8 PcM (M = Mg, CrCl 2 , Ru-Cl, Sc-Cl, SnCl 2 , and Pb), possible due either to the presence of two axial ligands, which block both sides of the phthalocyanine from association with TPP (M = CrCl 2 , Ru-Cl, Sc-Cl, SnCl 2 ), or due to the extreme non-planarity of the (dipPhO) 8 PcM macrocycle induced by the large metal cation which hindered heterodimer formation (M = Mg, Pb). It is a general feature of the (dipPhO) 8 PcM component of PNCs that it has a conical shape with the apex of the cone pointing into the void. The degree of curvature q can be defined by the angle between the planes of the two benzo units on the opposite sides of the phthalocyanine (Fig. ). The close cofacial association of TPP within the PNC reduces the angle of curvature of the (dipPhO) 8 PcM by an average of 12° relative to that of the same (dipPhO) 8 PcM without TPP (Fig. ). This flatening of (dipPhO) 8 PcM can be attributed to the strong interactions with TPP, which is highly planar in all PNCs obtained. In addition, any axial ligand bonded to the metal cation of (dipPhO) 8 PcM, which is forced into the cavity by the presence of the TPP, will pull the metal towards the cavity further reducing the conic deformation. The PNCs formed from (dipPhO) 8 PcIn-Cl provide an extreme example of the change in conical shape of the phthalocyanine on association with TTP with q reduced by 23° in PNC[cHO-In/vTPP] relative to PNC[In-vOH] (Fig. ). This is due to the large metal cation, which protrudes from the macrocyclic plane by ~1 Å and its -OH axial ligand both being forced into the cavity by the presence of the TPP. Efficient co-crystallisation implies that a heterodimer of (dipPhO) 8 PcM and TPP assembles in solution, similar to previously reported porphyrin-phthalocyanine supramolecular heterodimers. UV/visible absorption spectroscopy of an equimolar solution (10 -5 M) of (dipPhO) 8 PcH 2 and TPP in pure dichloromethane (DCM) shows no evidence of aggregation, however, with the addition of methanol (MeOH), the non-solvent for crystallisations, a broad peak at ~740 nm is observed, which is consistent with previously reported cofacial porphyrin/phthalocyanine heterodimers (Fig. ). Much clearer spectra supporting heterodimer formation (lmax = 725 nm) were obtained from 1:1 DCM:MeOH solutions of (dipPhO) 8 PcCu and TPP due to the well-defined, single Q-band of (dipPhO) 8 PcCu (l max = 680 nm) (Fig. ). This allowed the estimation of an (dipPhO) 8 PcCu/TPP association constant (K a ) of 1.4-1.6 x 10 5 M -1 for this solvent mixture. Therefore, there is clear evidence of efficient heterodimer formation in a similar mixed solvent system that was used for cocrystallisations. An NMR titration analysis involving the addition of TTP to (dipPhO) 8 PcH 2 to maintain a total concentration of 1 mM of combined macrocycle in CDCl 3 solution shows extreme broadening of peaks, which is characteristic of aggregation (Fig. ). This is particularly obvious for the internal protons for both macrocycles (Fig. ), which become so broadened that they are almost indistinguishable at an equimolar concentration.