To examine the influence of mixed substituents on the structural, electrochemical redox behavior of porphyrins, two new classes of beta-pyrrole mixed substituted free-base tetraphenylporphyrins H2(TPP(Ph)4X4) (X = CH3, H, Br, Cl, CN) and H2(TPP(CH3)4X4) (X = H, Ph, Br, CN) and their metal (M = Ni(II), Cu(II), and Zn(II)) complexes have been synthesized effectively using the modified Suzuki cross-coupling reactions. Optical absorption spectra of these porphyrins showed significant red-shift with the variation of X in H2(TPPR4X4), and they induce a 20-30 nm shift in the B band and a 25-100 nm shift in the longest wavelength band [Q(x)(0,0)] relative to the corresponding H2TPPR4 (R = CH3, Ph) derivatives. Crystal structure of a highly sterically crowded Cu(TPP(Ph)4(CH3)4).2CHCl3 complex shows a combination of ruffling and saddling of the porphyrin core while the Zn(TPP(Ph)4Br4(CH3OH)).CH3OH structure exhibits predominantly saddling of the macrocycle. Further, the six-coordinated Ni(TPP(Ph)4(CN)4(Py)2).2(Py) structure shows nearly planar geometry of the porphyrin ring with the expansion of the core. Electrochemical redox behavior of the MTPPR4X4 compounds exhibit dramatic cathodic shift in first ring oxidation potentials (300-500 mV) while the reduction potentials are marginally cathodic in contrast to their corresponding MTPPX4 (X = Br, CN) derivatives. The redox potentials were analyzed using Hammett plots, and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap decreases with an increase in the Hammett parameter of the substituents. Electronic absorption spectral bands of H2TPPR4X4 are unique that their energy lies intermediate to their corresponding data for the H2(TPPX8) (X = CH3, Ph, Br, Cl) derivatives. The dramatic variation in redox potentials and large red-shift in the absorption bands in mixed substituted porphyrins have been explained on the basis of the nonplanarity of the macrocycle and substituent effects.

Two ligand‐protected nanoscale silver moieties, [Ag46(SPhMe2)24(PPh3)8](NO3)2 and [Ag40(SPhMe2)24(PPh3)8](NO3)2 (abbreviated as Ag46 and Ag40, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag32S24P8, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag14 and a completely new core, Ag8, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT).

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The design and synthesis of novel fluorescent heterocyclic dyes is a “hotspot” research area, due to their favourable photophysical and electronic properties, which could allow huge advances in the fields of physics, chemistry and biology.

A symmetrical macrocyclic dizinc(II) complex (1) has been synthesized by using the ligand (L(1)) [μ-11,24-dimethyl-4,7,16,19-tetraoxa-3,8,15,20-tetraazatricyclo-[20.3.1.1(10,13)] heptacosa-1(25),2,7,9,11,13(27),14,20,22(26),23-decaene-26,27-diol]. A series of unsymmetrical macrocyclic dizinc(II) complexes (2-6) has been synthesized by Schiff base condensation of bicompartmental mononuclear complex [ZnL] [μ-3,16-dimethyl-8,11-dioxa-7,12-diazadicyclo-[1.1(14,18)] heptacosa-1,3,5(20),6,12,14,16,18(19)-octacaene-19,20-diolato)zinc(II)] with various diamines like 1,2-diamino ethane (L(2)), 1,3-diamino propane (L(3)), 1,4-diamino butane (L(4)), 1,2-diamino benzene (L(5)), and 1,8-diamino naphthalene (L(6)). The ligand L(1) and all the zinc(II) complexes were structurally characterized. To corroborate the consequence of the aromatic moiety in comparison to the aliphatic moiety present in the macrocyclic ring on the phosphate ester hydrolysis, DNA binding and cleavage properties have been studied. The observed first order rate constant values for the hydrolysis of 4-nitrophenyl phosphate ester reaction are in the range from 2.73 × 10(-2) to 9.86 × 10(-2) s(-1).The interactions of complexes 1-6 with calf thymus DNA were studied by spectroscopic techniques, including absorption, fluorescence, and circular dichroism spectroscopy. The DNA binding constant values of the complexes were found in the range from 1.80 × 10(5) to 9.50 × 10(5) M(-1), and the binding affinities are in the following order: 6 > 5 > 1 > 2 > 3 > 4. All the dizinc(II) complexes 1-6 effectively promoted the hydrolytic cleavage of plasmid pBR322 DNA under anaerobic and aerobic conditions. Kinetic data for DNA hydrolysis promoted by 6 under physiological conditions give the observed rate constant (k(obs)) of 4.42 ± 0.2 h(-1), which shows a 10(8)-fold rate acceleration over the uncatalyzed reaction of ds-DNA. The comparison of the dizinc(II) complexes 1-6 with the monozinc(II) complex [ZnL] indicates that the DNA cleavage acceleration promoted by 1-6 are due to the efficient cooperative catalysis of the two close proximate zinc(II) cation centers. The ligand L(1), dizinc(II) complexes 1, 3, and 6 showed cytotoxicity in human hepatoma HepG2 cancer cells, giving IC(50) values of 117, 37.1, 16.5, and 8.32 μM, respectively. The results demonstrated that 6, a dizinc(II) complex with potent antiproliferative activity, is able to induce caspase-dependent apoptosis in human cancer cells. Cytotoxicity of the complexes was further confirmed by the lactate dehydrogenase enzyme level in HepG2 cell lysate and content media.