## 3 Results and Discussion
### Thermal and Mesomorphic Properties
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **Vmol** & \(d_{\text{lam}}\) & \(N_{\text{molL}}\) & \(N_{\text{arL}}\) & \(N_{\text{chl}}\) & \(q_{\text{ch}}\) \\
**Phase, \(T\)** & \(\rho\) & \(d_{\text{lam}}\) & \(A_{\text{mol}}\) & \(S_{\text{ZnAr}}\) & \(S_{\text{ch}}\) & \\ \hline
**Zn_tpy** & 27,530.99 & 29.31 & 2 & 1 & 2 & 1.41 \\ SmA, 85 & & & 188 & 94 & 31.3 & \\ \hline
**Zn_tpy** & 2781 & 28.89 & 2 & 1 & 2 & 1.43 \\ SmA, 100 & 0.98 & & 192 & 96 & 32.1 & \\ \hline \hline \end{tabular} \(T\), temperature of the measurement (\({}^{\circ}\)C); Vmol, calculated molecular volume (Å\({}^{3}\)); \(\rho\), density (g/cm\({}^{3}\)); \(d_{\text{lam}}\), lamellar periodicity (Å\({}_{3}\)); \(N_{\text{molL}}\), number of molecular layers per lamella; \(A_{\text{mol}}=N_{\text{molL}}\times V_{\text{mol}}/d\), molecular area (Å\({}^{2}\)); \(N_{\text{sat}}\), number of aromatic layers per lamella (\(N_{\text{sat}}=1\) for monolayer arrangement); \(S_{\text{ZnAr}}=(N_{\text{sat}}/N_{\text{molL}})\times A_{\text{mol}}\), surface per Zinc complex (Å\({}^{2}\)); \(N_{\text{chlL}}\), number of chain layers per lamella (\(N_{\text{chlL}}=2\) for non-inter-interdigitated chains); \(S_{\text{ch}}=(N_{\text{chl}}/N_{\text{molL}})\times A_{\text{mol}}/n_{\text{ ch}}\), surface per chain (Å\({}^{2}\)); \(n_{\text{ch}}=6\) being the number of peripheral chains per molecule; \(q_{\text{ch}}=S_{\text{ch}}/\sigma_{\text{ch}}\), chain packing ratio, \(\sigma_{\text{ch}}=(26.5616+0.020237)/1.27\) (Å\({}^{2}\)) being the cross-sectional area of a molten chain [51].  
\end{table} 
Table 2: Geometrical mesophases parameters. Figure 3: Idealized supramolecular representation of the **Zn_tpy** complexes in the SmA phase through self-assembly of aromatic and metallic moieties into monolayers (various possibilities of head-to-head arrangements are shown, with, in some cases, the possibility of larger interdigitation) alternating with molten chains (aliphatic chains continuum is shown in pale blue); \(d_{\text{lam}}\) and \(A_{\text{mol}}\) are the lamellar periodicity and molecular area, and Dar is the average separation between [**Zn_tpy**] moieties, \(D_{\text{ar}}\sim\surd(A_{\text{mol}}/\pi)\) (see Table 2). organization (Figure 3). The formation of such lamellar structure implies that the molecular packing within the aromatic layer matches the high overall cross-sectional area of the six pending chains (6\(\times\)\(\sigma_{\rm ch}\)\(\approx\) 135 A\({}^{2}\)). This condition is realized through a monolayer configuration alternating terpyridine rings and gallate segments in the layer plane. This arrangement, which is also found in CSD-BETWOO and otherwise explains the in-plane periodicity Dar, offers a high molecular cross-section (S\({}_{\rm ZnAr}\) = 87 A\({}^{2}\) in CSD-BETWOO and S\({}_{\rm ZnAr}\)\(\approx\) 95 A\({}^{2}\) in **Zn_tpy**, Table 2). Above all, it allows sharing alkyl substituents between both adjacent layers, and thus elevates the molecular area to A\({}_{\rm mol}\)\(\approx\) 190 A\({}^{2}\), which even exceeds the requirement for alkyl chains (q\({}_{\rm ch}\)). This discrepancy is, however, easily compensated by a higher degree of the folding of the chains, to the cost of more diffuse interfaces and of a lower efficient nanosegregation between antagonistic moieties. This effect should contribute to the narrowness of the smectic range and to the difficulty to detect the lamellar higher order reflections. The reduction of the molecular structure beside easing the synthesis has a significant influence on the supramolecular organisation in the mesophase: the non-substituted coordination complex described herein **Zn_tpy**, arranges into smectic phases while the apical substitution of the typ ligand direct the self-assembly into room temperature hexagonal mesophases, as previously reported for **Zn_1-4**[27; 28] (Figure 1).