Alessandro D'Urso

Interactions of a Tetraanionic Porphyrin with DNA: from a Z-DNA Sensor to a Versatile Supramolecular Device

The anionic nickel(II) porphyrin NiTPPS is able to selectively sense the spermine induced left-handed Z-form of DNA while it is completely silent in the presence of right-handed B-DNA. Interactions between the DNA and the porphyrin can be easily modulated by pH and temperature. The resulting Z-DNA-porphyrin-spermine complex behaves as a supramolecular reversible information storage system and as a reversible AND logic gate.

Vortexes and Nanoscale Chirality

Contents: • Experimental details of the CD experiments on the halved cuvettes.

Anion-assisted supramolecular polymerization: from achiral AB-type monomers to chiral assemblies.

Control over the self-assembly process of monomeric species by functional group modulation is highly desirable in the context of supramolecular polymer design. These materials, unlike covalently linked polymers, consist of monomeric arrays held together by reversible and highly directional noncovalent bonds. Owing to the dynamic and reversible nature of noncovalent interactions, supramolecular polymers display unique topologies and unconventional properties (such as stimuli responsiveness and self-healing) and are thus becoming cutting-edge species in modern materials science. Multiple hydrogen bonds, metal–ligand coordination, and p–p stacking are, by far, the most common weak forces used for engineering supramolecular polymers. Recently, however, oligomeric and polymeric architectures based on host–guest inclusion complexes have started to become more and more popular. Within this research frame, we have recently described a pH-responsive aminododecyloxy-calix[5]arene derivative (C5-NH2) that, upon exposure to a variety of acids, selfassembles into linear oligomers. Protonation activates the two latent self-complementary binding sites of this heteroditopic monomer precursor (i.e. a preorganized cone-shaped p-rich calix[5]arene cavity and a linear alkylamine pendant chain) and, according to a well-established host–guest recognition pattern, which involves a concerted set of weak interactions (NH···O, CH–p, cation–p), supramolecular oligomer formation readily occurs. However, because of the intrinsically saline nature of the monomers used, the growth of these supramolecular assemblies was found to be aniondependent. More specifically, the looser the ion-pairing interactions between the ammonium monomer and its counterion, the higher the degree of polymerization observed. Although ion-pairing effects have been analyzed extensively in relation to simple one-to-one host–guest systems, to the best of our knowledge they have not yet been examined in the context of supramolecular polymers derived from charged monomers. Elegant examples of polymeric species derived from crown ethers, cryptands, cyclodextrins, cucurbiturils, calixarenes, 16] and resorcinarenes have been described, but in none of these instances—neither ABtype (self-complementary heteroditopic) 12a,b, 13a, 17a] nor AA/BB-type (complementary homoditopic) 15, 17b] systems—has the role of the counterion in the growth of the polymer or the tuning of the supramolecular properties been addressed. Drawing on our earlier investigations on the simultaneous complexation of cations and anions 18] and on the design of heteroditopic and heterotetratopic receptors in an attempt to override the drawback of ion-pairing effects in AB-type salt monomers, we have now incorporated an ancillary anion-binding site (namely a ureido moiety) into calix[5]arene C5-NH2 with the aim of facilitating salt dissociation and ultimately making polymer formation more efficient. In this communication we demonstrate that the addition of this anion-binding site to the monomer scaffold is beneficial to the supramolecular polymerization process and, most importantly, we show that modulation of the properties [*] Dr. C. Capici, Dr. G. Gattuso, Dr. A. Notti, Prof. M. F. Parisi Dipartimento di Chimica Organica e Biologica Universit di Messina Viale F. Stagno d’Alcontres 31, 98166 Messina (Italy) E-mail: ggattuso@unime.it mparisi@unime.it

Chiral sign selection on the J‐aggregates of diprotonated tetrakis‐(4‐sulfonatophenyl)porphyrin by traces of unidentified chiral contaminants present in the ultra‐pure water used as solvent

Traces of biological contaminants that cannot be detected, but are expected to be present, in ultra-pure water suffice to select the emerging chiral sign in the spontaneous mirror symmetry breaking that takes place during the formation of the J-aggregates of the amphiphilic diprotonated tetrakis-(4-sulfonatophenyl)porphyrin (H(4)TPPS(4)(2-)). This is demonstrated by competition experiments with a chiral cationic surfactant. The sensitivity of the detection depends on the hierarchical control of the H(4)TPPS(4)(2-) self-aggregation.

Reversible “Chiral Memory” in Ruthenium Tris(phenanthroline)–Anionic Porphyrin Complexes

In the last few years, transfer and memory of chirality have been attracting growing interest for potential technological applications. In general, this phenomenon occurs through two steps: 1) transfer of chirality from a chiral template to an achiral covalent or noncovalent “polymeric” species and 2) “removal” of the chiral cast which leaves its chirality permanently imprinted on the “polymer”. The chiral memory relies on the kinetic inertness of the “polymeric” species and most examples rely on systems that have a “static” memory: that is, once imprinted and memorized, chirality becomes an intrinsic but nontunable feature of the complex. Only recently has a system with a “dynamic memory” for which it is possible to cyclically store and release the “memorized chirality” been reported. We report herein a new and more intriguing “dynamic” supramolecular memory system (SuMe). We have recently reported that the L and D enantiomers of [Ru(1,10-phenanthroline)3] 2+ ([Ru(phen)3] , lmax = 262 nm, Figure 1) induce chiral aggregation of various achiral anionic porphyrins. Our interest in this complex system stems from two considerations. Firstly, porphyrins are ideal building blocks for supramolecular architectures because of their unique spectroscopic properties (extinction coefficients of ca. 10 and intense emission signals, the position and intensity of which can be tuned by insertion of a central metal ion) and the possibility of modulation of their self-aggregation. Secondly, ruthenium (II) complexes can transfer two kind of molecular information—energy and chirality—to porphyrins and their aggregates. 5] The interaction between meso-tetrakis(4-sulfonatophenyl)porphine (H2TPPS4, lmax = 412 nm, Figure 1) and an equimolar amount of [Ru(phen)3] 2+ (pH 6.0, NaCl (0.3m)) is indicated by variations in the absorption spectra of both [Ru(phen)3] 2+ and H2TPPS4. The strongest evidence of interaction, however, comes from the appearance of an induced circular dichroism (ICD) band in the absorption region (Soret band) of the achiral porphyrin (Figure 2). The relationship between chirality of the cationic metal complex and that transferred to the anionic porphyrins is straightforward because interactions of H2TPPS4 with the Land D[Ru(phen)3] 2+ lead to mirror-image ICD signals (Figure 2). At a pH value lower than 3 and in the presence of millimolar concentration of salt, the protonated species of H2TPPS4 (H4TPPS4, pKa 5, lmax = 436 nm) is zwitterionic and self-assembles to give both face-to-face (H, lmax = 422 nm) and edge-to-edge aggregates (J, lmax = 490 nm, Figure 3). Yashima and co-workers have shown very Figure 1. Structure of the anionic porphyrin H2TPPS4 and of the L and D enantiomers of [Ru(phen)3] .

Interaction of Tricationic Corroles with Single/Double Helix of Homopolymeric Nucleic Acids and DNA

In this manuscript a multitechnique approach is proposed to characterize the interaction between new tri-N-methylpyridyl corrole (TMPC) and its germanium(IV) derivative (GeTMPC), with single- and double-stranded nucleic acid homopolymers and calf thymus DNA. The specificity of each spectroscopic technique has been exploited to analyze the different aspects of corrole binding. Noteworthy, this approach allows us to distinguish between H aggregation of TMPC in the presence of polyriboadenilic acid (poly(rA)) and J aggregates in the presence of polyribocytidinic acid (poly(rC)) as well as to identify the formation of GeTMPC dimers in the presence of single-stranded poly(rA) and pseudointercalation with single-stranded poly(rC).

Z-DNA Recognition in B-Z-B Sequences by a Cationic Zinc Porphyrin

For the first time it has been shown by spectroscopic studies such as circular dichroism and UV/Vis that cationic zinc porphyrin serves as a selective spectroscopic sensor that is able to recognize short left-handed Z-DNA tracts embedded in the B-Z-B sequences.

Sequence, Stoichiometry, and Dimensionality Control in Porphyrin/Bis‐calix[4]arene Self‐Assemblies in Aqueous Solution

The use of a water-soluble octacationic bis-calix[4]arene with divergent cavities (BC(4)) as a templating agent for the assembly of a tetraanionic porphyrin (CuTPPS) has allowed the noncovalent synthesis of 2D or 3D multiporphyrin assemblies. Self-assembly of CuTPPS and BC(4) molecules proceeded under hierarchical control in a stepwise fashion to yield discrete and isolable supramolecular nanostructures containing up to 33 molecular elements (i.e., the CuTPPS/BC(4) 17:16 assembly, obtained in less than three hours). The formation of these species could be conveniently monitored by means of UV/Vis spectroscopy by following the absorbance of the Soret band at 412 nm. In particular, the attainment of the pivotal CuTPPS/BC(4) 5:4 species with a cruciform structure, as the key fork-point intermediate for the subsequent formation of the higher 2D and 3D assemblies, has been demonstrated by light-scattering studies and by an unequivocal synthesis of mixed-porphyrin/calixarene 5:4 species involving the use of two different types of metallated porphyrins, namely CuTPPS and MnTPPS. The remarkable stability of these assemblies permits a stepwise synthesis that makes it possible to choose the desired porphyrin sequence.

Chiroptical properties of anionic and cationic porphyrins and metalloporphyrins in complex with left-handed Z-DNA and right-handed B-DNA

We report the chiroptical signature and binding interactions of cationic (meso-tetrakis(4-N-methylptridyl)porphyrin, 2HT4) and anionic (meso-tetrakis(4-sulfonatophenyl)porphyrin, 2HTPPS) porphyrins and their zinc(II) and nickel(II) derivatives (ZnT4, ZnTPPS, NiT4, and NiTPPS) with right-handed B-form and two forms of left-handed Z-form of alternating guanine-cytosine polydeoxynucleotide poly(dG-dC)2. NiTPPS is able to spectroscopically discriminate between spermine-induced Z-DNA and Co(III)-induced Z-DNA via new induced circular dichroism signal in the visible region of the electromagnetic spectrum.

Hierarchical dependence of porphyrin self-aggregation: controlling and exploiting the complexity

Self-aggregation processes are rarely reproducible owing to their dependence on various experimental parameters (aging of stock solutions, their concentration, concentration of working solutions, ionic strength, etc.). However, by enucleating the dependence from one parameter (in this case, the dependence of aggregation from the concentration of the working solutions), it has been possible to hierarchically control self-aggregation of the protonated form of tetrakis-(4-sulfonatophenyl)-porphyrin.