Structure-property or structure-function relationships are the basis for molecular design and engineering to develop new compounds with custom-tailored functionality. Porphyrin, a nitrogen-functionalized pseudo-D4h-symmetric 18π aromatic macrocycle, is arguably one of the most important naturally occurring small cyclic molecules, whose metal complexes enable a myriad of enzymatic chemical transformations as essential cofactors and serve as key signalling and transportation substances in a vast array of living organisms . Thus, porphyrins have inspired decades of intense research on their structural modification, which has led to a variety of porphyrinoids and their metal complexes in order to explore new molecular functions . Among the related macrocycles that feature four inwardly oriented nitrogen atoms, structures are usually characterized according to the number of protonated and positively charged nitrogen atoms and the overall architecture (Fig. ). Porphyrin exhibits a planar structure with two N-H moieties; the truncation of one meso-carbon atom gives planar corrole with three N-H moieties, which acts as a trivalent ligand to give rise to a variety of metal complexes with rich chemistry . The use of an indole rather than a pyrrole moiety to construct the N4 macrocycle furnishes tetraindole with four N-H moieties, which is reminiscent of a porphyrinogen and structurally deviates slightly from planarity . Tetraindole is susceptible to oxidation, which causes it to act as a planar divalent ligand similar to porphyrin. In contrast, the tetrapyrrolic macrocycle calix [4]pyrrole, which is characterized by a lack of global conjugation, exhibits a 3D architecture with several preferred conformations depending on the chemical environment. This macrocycle , which was discovered over 100 years ago, has been reported to exhibit exceptional anionreceptor properties , significantly expanding its potential applications in the context of host-guest chemistry . Additionally, a calix-type 3D N4 macrocycle that features four pyridyl nitrogen atoms, calix [4]pyridine, has been reported as a neutral ligand for metal cations , and the chemistry of its aza- derivatives (X = NR′) was later broadly expanded . In stark contrast, quinoline has not yet been systematically exploited as a key constituent in such macrocycles. In 2019, we disclosed TriQuinolines (TQs), i.e., pseudo-planar cyclic quinoline trimers concatenated at the 2 and 8 positions in a head-to-tail fashion (Fig. ) . While TQs share structural characteristics with their more flexible counterparts, i.e., tricyclic aminopyridines, their behaviour is considerably different: TQs exhibit unique physicochemical properties, e.g., extraordinary proton affinity, CH-π/π-π supramolecular complexation, and DNA intercalation. This is presumably due to the increased structural rigidity that arises from the use of the quinoline unit. We reasoned that incorporating one more quinoline unit into a TQ architecture would deliver the unprecedented non-flat N4 macrocycle TEtraQuinoline (TEQ). Herein, we report the synthesis and detailed physicochemical studies on TEQs, highlighting the explicit differences relative to (aza)calix [4]pyridines, which presumably originate from the highly rigid nature of TEQs. The steep saddleshaped structure acquires chirality upon partial desymmetrization by substitution and is remarkably resistant to racemization. TEQs become strongly emissive in the presence of protons or Zn(II) cations with a high quantum yield, and their structural chirality enables them to act as circularly polarized luminescence (CPL) emitters . Metal complexation was systematically surveyed, culminating in the identification of TEQ/Fe 2+ as a promising oxidation catalyst system that operates effectively at catalyst loadings as low as 0.1 mol%.