The porphyrin-ferrocene conjugates ( P-nFc; n = 1, 2 and 4 ), which are simple examples of a donor-acceptor charge separation system, were synthesized. Their photoindued intramolecular and intermolecular processes have been investigated by time-resolved emission and nanosecond transient absorption techniques. Upon excitation of the porphyrins ( H 2P and ZnP ) moieties, an efficient fluorescence quenching of the excited singlet porphyrin is observed. It was found that the quenching efficiency increases with increasing number of attached ferrocene moieties and solvent polarity. The main quenching pathway involves (i) electron transfer from ferrocene to the singlet excited porphyrin and (ii) the heavy-atom effect.
The syntheses, characterizations and transformations of three tetraphenylporphyrins derived from methoxymethylated benzaldehyde 3 are described. Benzaldehyde 3 reacted with pyrrole under Lewis acid catalysis to give dipyrromethane 4 which was used as precursor in porphyrin syntheses. Porphyrins 6, αα-7 and αβ-7 were obtained using conditions for sterically encumbered benzaldehydes, with αα-7 and αβ-7 being atropisomers. The methoxymethyl groups of 6, αα-7 and αβ-7 were transformed into bromomethyl substituents (porphyrins 8, αα-9 and αβ-9) which were easily modified by nucleophilic reaction with the azide anion. Porphyrin azide 10 was subjected to a Staudinger phosphazene formation with triphenylphosphine. Subsequent reaction of the porphyrin phosphazene 12 with carboxylic acids gave acetamide 13, benzamide 14, and ferrocene carboxamide 15, respectively. Kornblum oxidation of monobromomethyl porphyrin 8 gave the formyl derivative 16.
A ruthenium complex [Ru(H 2 O){Et 2 NpyS 4 (O 3 ) 2 }] Á (4) containing sulfinates, sulfenates S-donors, and water as co-ligand has been synthesized from oxidation of hydrazine complex [Ru(N 2 H 4 )(Et 2 NpyS 4 )] (3) and completely characterized with X-ray structural analysis [Et 2 NpyS À2 4 = 4-(diethylamino)-2,6-bis[(2-mercaptophenyl)thiomethyl]pyridine(2À)]. Complex 4 exhibits distorted octahedral coordination of the ruthenium center and the d [Ru-S sulfinates ] and d [Ru-S sulfenates ] are almost equivalent. The average d [S-O sulfinate ] at 148.0 pm is ca 10 pm longer than the average d [S-O sulfenate ] at 138.0 pm. The sulfinates IR(KBr) bands are located in the range 1132-1113 cm À1 as two band sets, (SO) asym and (SO) sym , whereas the sulfenates show a single absorbance at approximately 882 cm À1 . The lower frequency of the (SO)stretches of the sulfenates as compared to that of their sulfinate rivals indicates a weaker S-O bond in the sulfenates and is consistent with X-ray crystal structure data (vide infra). Oxidation of the dithiol ligand Et 2 NpyS 4 -H 2 (1) under the same condition afforded the disulfide, in this case forming a macrocyclic ligand S,S-Et 2 NpyS 4 (2) as is evidenced by an X-ray crystal structure determination. Thus, the oxidation of 3 involves activation of either the oxygen or thiolate by the ruthenium center.
Two iron(II) complexes, [Fe II (py t BuN 3 ) 2 ](FeCl 4 ) (1) and [Fe II (py t BuMe 2 N 3 )Cl 2 ] (2), with sterically constrained py t BuN 3 and py t BuMe 2 N 3 chelate ligands (py t BuN 3 = 2,6-bis-(aldiimino)pyridyl; py t BuMe 2 N 3 = 2,6-bis-(ketimino)pyridyl), have been synthesized and characterized by elemental analysis, IR, UV-vis spectra and preliminary X-ray single-crystal diffraction. The latter revealed that Fe(II) in 1 is six-coordinate by six nitrogen donors from two bisiminopyridines in a distorted octahedron. Complex 2 reacts with thiourea with a second-order rate constant k 2 = (2.50 ± 0.05) × 10 -3 M -1 s -1 at 296 K, and the reaction seemed to be slow. In a similar way, the interaction of 2 and DNA was studied by fluorescence and absorption spectroscopy. The results revealed that 2 caused fluorescence quenching of DNA through a dynamic quenching procedure. The binding constants K A , K app and K SV as well as the number of binding sites between 2 and DNA were determined.
The objective of this study was to improve the antibacterial activities of chitosan via N-alkyl substitution using 1-bromohexadecane. Mono and di substitution (Mono-NHD-Ch and Di-NHD-Ch) were prepared and characterized using FT-IR, HNMR, TGA, DSC, and SEM. Elemental analysis shows an increase in the C/N ratio from 5.45 for chitosan to 8.63 for Mono-NHD-Ch and 10.46 for Di-NHD-Ch. The antibacterial properties were evaluated against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus cereus. In the examined microorganisms, the antibacterial properties of the novel alkyl derivatives increased substantially higher than chitosan. The minimum inhibitory concentration (MIC) of Mono-NHD-Ch and Di-NHD-Ch was perceived at 50 μg/mL against tested microorganisms, except for B. cereus. The MTT test was used to determine the cytotoxicity of the produced materials, which proved their safety to fibroblast cells. The findings suggest that the new N-Alkyl chitosan derivatives might be used as antibacterial alternatives to pure chitosan in wound infection treatments.
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