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Two octahalogenated nickel(II) hydroxyphenylporphyrins were synthesized and characterized as to their electrochemical and spectroscopic properties as well as their reactivity in neutral, acidic, and basic nonaqueous media. The newly synthesized complexes are represented as NiPorCl

Interactions of anionic guests with a tritopic peripherally functionalized conjugated calix[4]pyrrole host (1) prepared using a regioselective synthetic method is reported. The regioselectivity of synthesis relies on selective N-alkylation of the calix[4]pyrrole caused by peripheral substitution of one pyrrole group with subsequent N-alkylation at the opposing pyrrole group termed by us ‘knock-on’ regioselectivity. The resulting host molecule exhibits anion interactions with common chloride and nitrate anions enhanced by an order of magnitude over the parent conjugated calix[4]pyrrole. Combined analysis of 1H NMR and UV-vis spectroscopic titration data enabled an evaluation of binding strengths of anions with the host KA in a binding model where the salt dissociation process is also incorporated in the form of its dissociation constant Kd. Anions could be classified as two types based on their interactions with 1: Type A anions (chloride, nitrate, perchlorate, hydrogensulphate) associate as 1 : 1 complexes through hydrogen bonding while interactions involving Type B anions (acetate, fluoride, dihydrogenphosphate) are complicated by host deprotonation and/or countercation association. Hosts based on rim-functionalized calix[4]pyrroles such as 1 represent a promising new family of chromophores for estimation of biologically relevant anions or other species.

Nitrogen and phosphorus-containing ions such as ammonium, nitrates and phosphates are anthropogenic pollutants while ammonium nitrate may be diverted for nefarious purposes in improvised explosive devices. Crown ether-oxoporphyrinogen conjugates (OxP-crowns) are used to selectively detect nitrates, especially their ion pairs with K+ and NH4 + , based on ion pair complexation of OxP-crowns under phase transfer conditions. The presence of phosphate and carbonate lead to deprotonation of OxP-crowns. OxP-1N18C6 is capable of extracting ion pairs with nitrate from aqueous phase leading to a selective chromogenic response. Deprotonation of the OxP moiety leads to [OxP- ]-1N18C6[K+ ] and is promoted by crown ether selective cation binding coupled with hydration of basic oxoanions, which are constrained to remain in the aqueous phase. This work illustrates the utility of molecular design to exploit partitioning and ion hydration effects establishing the selectivity of the chromogenic response.

Copper(II) or Nickel(II) complexes of 5,10,15,20-tetrakis(3,4-dioxo-5-t-butylcyclohexa-1,5-dienyl)porphyrin (diOxPM, M = Ni, Cu) exhibited a hypsochromic shift in the B-band as compared to the respective 5,10,15,20-tetrakis(3,5-di-t-butyl-4′-hydroxyphenyl)porphyrin (H2-dtBTPP) and meso-tetrakis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadienylidene)porphyrinogen (OxP). Thorough investigation of the electrochemical properties of diOxPM (M = Ni, Cu), OxP and H2-dtBTPP lead us to the important observation that the first reduction of diOxPM (M = Ni and Cu) is very much anodically shifted (ΔEredn = 1.1 V) as compared to that of M-dtBTPP (M = Cu or Ni) due to the presence of the strongly electron withdrawing cyclohexadienyl groups. These electron-deficient meso-tetrakis(3,4-benzoquinone)-substituted Ni(II) and Cu(II) porphyrins exhibited very high binding constants (1.5 × 109–2.5 × 107 M−2) with F− and CN− and can be used to distinguish them from other anions by UV-Vis spectrophotometry. Solvatochromism was combined with anion binding in an attempt to provide the axial ligation mechanism of CN− and F− ions. These highly electron deficient porphyrins act as F− and CN− chemosensors in nonaqueous media. However, these porphyrins detect only CN− ions in an aqueous medium but remain insensitive towards F− ions due to high solvation of F− ions in water.

Singlet oxygen (1O2) is an excited state of the dioxygen molecule with higher reactivity compared to the ground electronic state. Therefore, singlet oxygen is an important species used for oxidation of organic compounds, degradation of environmental pollutants, inactivation of bacteria or treatment of tumours. Metal-organic frameworks (MOFs) are suitable as carriers of 1O2 photosensitizers because of the permeability of their porous structure to gas molecules and effective prevention of aggregation of the photosensitizer chromophores. Moreover, the character of MOFs enables easy preparation of multifunctional materials combining 1O2 generation with other properties. In this review we summarize recent advances in the development of MOFs for 1O2 generation. We focus on the three main fields of application of these materials: oxidation of organic compounds, degradation of pollutants and photodynamic therapy. Each of these fields has its own specific requirements, which is reflected in the design of appropriate materials.

We utilized the potential applications of 1,8-naphthyridine-based sensors for the detection of various nitroaromatics such as picric acid (PA), 3-nitrophenol (NP), 2,4-dinitrotoluene (DNT), 1,3-dinitrobenzene (DNB), 4-nitrotoluene (NT), nitrobenzene (NB) and nitromethane (NM). Among the various nitroaromatic analogues, nap-OH (1) and nap-Cl (2) sense picric acid (PA) much more efficiently and with very low detection limits (1.12 and 0.96 ppm, respectively), owing to favourable electron and/or energy transfer mechanisms along with potential electrostatic interactions. Interestingly, both sensors 1 and 2 detect PA in aqueous media (H2O/CH3OH, 8 : 2) with the same quenching efficiency as in neat CH3OH, resulting in cheap, sensitive and environmentally friendly detection methodology. Therefore, use of these molecules for picric acid detection in aqueous and methanolic solutions, having low detection limits along with exceptional quenching constants (kSV) meets the present need. In addition, sensors 1 and 2 exhibit instant visualization of trace amounts of PA in both the solid-state and when using test strips.

Dicyanovinyl appended β-pyrrole substituted porphyrins have been synthesized and utilized as chemodosimeters for ratiometric and colorimetric sensing of cyanide ions. In addition to meso-tetraphenylporphyrin (TPP) based system, we have designed and synthesized octaphenylporphyrin (OPP) based moderately nonplanar systems. These systems also depicted effective π-conjugation between the pyrrole ring and its olefinic substituent which is reflected in the UV-vis absorption spectra as the red-shifting of both Soret and Q-bands and possibly the splitting of the absorption Soret band. This article describes the single crystal X-ray structure, electronic spectral and electrochemical redox properties of these porphyrin chemodosimeters. The stable anionic-porphyrin species formed after addition of CN− ions has a blue shifted unperturbed absorption spectrum due to the disruption of electronic resonance and charge-transfer interactions between the β-dicyanovinyl acceptor and porphyrin core. The probes exhibited excellent selectivity towards CN− over other anions such as F−, Cl−, Br−, NO3−, H2PO4−, AcO−, I−, HSO4−, ClO4− and PF6−. The action of the chemodosimeters were investigated by 1H-NMR titrations, ESI-mass spectrometry, electrochemical studies and DFT calculations which supported the formation of cyanide addition adduct (porphyrin–CN)−. These chemodosimeters depicted lowest detection limit (LOD) of 0.023–0.082 ppm, which is very much lower than the permissible limit (0.2 ppm) and other porphyrinoids reported till date. These porphyrins are also able to detect cyanide ions in (9:1, v/v) CH3CN:H2O mixture with low detection limits thereby providing practical applicability of these chemodosimeters.

Two new receptors viz. 2-bromoacetamido-5,7-dimethyl-1,8-naphthyridine (1a) and 2-chloroacetamido-5,7-dimethyl-1,8-naphthyridine (1b) containing 1,8-naphthyridine as fluorophore unit have been designed and synthesised. These receptors exhibited very high selectivity for F− ions among the various anions tested such as H2PO4−, OAc−, Cl−, Br−, I−, HSO4−, PF6−, ClO4−, BF4− and NO3− owing to anion-induced deprotonation of the amide NH by F− ions. Among the various cations tested (Na+, Ag+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ and Mn3+), 1a exhibited selective detection of Hg2+ ions by binding with N1 and N8 atoms of the naphthyridine moiety. Receptor 1a has been explored as a dual-ion detector for F− and Hg2+ ions in two contrasting modes (fluorescence ‘turn-on’ and ‘turn-off’) which is supported by spectroscopic and lifetime measurements. 1a exhibited lower detection limits for F− (0.4 ppm) and Hg2+ (2.4 ppm) ions. These receptors were recovered from anionic species of 1a formed after addition of F− ions by treating with protic solvents such as CH3OH. The mode of binding was also confirmed by spectroscopic and DFT studies. The chemical inputs of F− and Hg2+ ions generate an output which satisfies the condition of two-input INHIBIT logic operators.

β-Functionalization of meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin with electron acceptors such as formyl and dicyanovinyl has been reported for the first time. 2-Formyl-5,10,15,20-tetrakis(3',5'-di-tert-butyl-4'-hydroxyphenyl)porphyrinatocopper(ii) (Cu-TDtBHPP-CHO) crystallizes in the triclinic space group P1[combining macron], [a = 10.8479(4) A, b = 14.6207(5) A, c = 15.9745(5) A, V = 2198.97(13) A3] and exhibits an almost planar structure and a square planar geometry. β-Formyl/dicyanovinyl substituted porphyrins such as Cu-TDtBHPP-CHO, Ni-TDtBHPP-CHO, Cu-TDtBHPP-MN (1), Ni-TDtBHPP-MN (2) and H2-TDtBHPP-MN (3) exhibited red-shifted optical absorption features (Δλmax = 13-40 nm) in CH2Cl2 compared to the corresponding MTPPs. β-Dicyanovinyl substituted porphyrins were developed as a quantitatively operating 'lab-on-a-molecule' for the visual detection of F- and CN- ions. Having a CN- ion responsive dicyanovinyl moiety and a F- ion responsive redox-active 3,5-di-tert-butyl-4-hydroxyphenyl groups, they detect F- and CN- ions simultaneously by switching unique structural changes between porphyrin, porphodimethene and porphyrinogen along with distinct colour changes which were monitored by UV-Vis-NIR, fluorescence and NMR spectroscopic techniques.