Structural features of neutral and cationic cyclams

Ambiguous Faces of Water-Based Inclusion Compounds: L4(4)8(8) Intercalato-Clathrate Hydrate of Pt(II) Complex

Clathrate hydrates are among the most intensively studied H-bond inclusion compounds. Despite the broad definition for this class of compounds, their meaning commonly refers to closed polyhedral nanocages that encapsulate small guest molecules. On the other hand, larger solutes enforce another type of encapsulation because of the solute size effect. Herein, we report a series of structures containing various molecules encapsulated by intercalated water layers constructed of polycyclic moieties of L4(4)8(8) topology. We parametrized the corrugation of individual layers and characterized interactions governing their formation. We suggested that these could be categorized as two-dimensional clathrates based on the character of intra-layer interactions and the effects observed between entrapped molecules and water-based intercalators.

Investigations into the Structure/Antibacterial Activity Relationships of Cyclam and Cyclen Derivatives

A series of cyclam- and cyclen-derived salts are described in the present work; they were designed specifically to gain insights into their structure and antibacterial activity towards Staphylococcus aureus and Escherichia coli, used respectively, as Gram-positive and Gram-negative model organisms. The newly synthesized compounds are monosubstituted and trans-disubstituted tetraazamacrocycles that display benzyl, methylbenzyl, trifluoromethylbenzyl, or trifluoroethylbenzyl substituents appended on the nitrogen atoms of the macrocyclic ring. The results obtained show that the chemical nature, polarity, and substitution patterns of the benzyl groups, as well as the number of pendant arms, are critical parameters for the antibacterial activity of the cyclam-based salts. The most active compounds against both bacterial strains were the trans-disubstituted cyclam salts displaying CF₃ groups in the para-position of the aromatic rings of the macrocyclic pendant arms. The analogous cyclen species presents a lower activity, revealing that the size of the macrocyclic backbone is an important requirement for the antibacterial activity of the tetraazamacrocycles. The nature of the anionic counterparts present on the salts was found to play a minor role in the antibacterial activity.

New Cyclams and Their Copper(II) and Iron(III) Complexes: Synthesis and Potential Application as Anticancer Agents

New cyclam derivatives (HOCH₂ CH₂ CH₂ )₂ (PhCH₂ )₂ Cyclam and (HOCH₂ CH₂ CH₂ )₂ ( 4 - CF 3 PhCH₂ )₂ Cyclam, as well as their Cu^II and Fe^III complexes, were synthesized and characterized and their stability in cellular media was assessed. The cytotoxic effect of all compounds was examined on human cervical cancer (HeLa) cells, revealing strong anticancer activity. After 24 h, only complexes with the (HOCH₂ CH₂ CH₂ )₂ ( 4 - CF 3 PhCH₂ )₂ Cyclam ligand are cytotoxic, whereas after incubation for 72 h all compounds show significant antiproliferative effects. Notably, compounds containing 4 - CF 3 PhCH₂ pendant arms on the cyclam ring revealed the most activity, with cytotoxicity values up to 12 times higher than those of cisplatin. All metal complexes seem to induce cell death through the formation of reactive oxygen species.

Synthesis, antimicrobial activity and toxicity to nematodes of cyclam derivatives

The antimicrobial activity and toxicity to nematodes of the cyclam salt [H₂{H₂(^4-CF₃PhCH₂)₂Cyclam}](CH₃COO)₂⋅(CH₃COOH)₂ were evaluated. Estimated minimum inhibitory concentrations (MICs) of 9, 261 and 15 µg/mL were obtained for Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, respectively. For selected Candida spp., the estimated MICs obtained ranged from 32 µg/mL to 63 µg/mL. Bactericidal activity was demonstrated but the compound was not reliably fungicidal. Concentrations of the cyclam salt up to 32 µg/mL did not significantly affect survival of the nematode Caenorhabditis elegans; however, concentrations equal or above this value significantly affected nematode survival in a dose-dependent manner.