A naphthalene benzimidazole-based chemosensor for the colorimetric and on-off fluorescent detection of fluoride ion.

A novel naphthalene benzimidazole (NBI)-based chemosensor (D2) was developed for fluoride ion (F-) detection. The absorption spectrum of D2 changed dramatically from yellow to blue in the visible region accompanied with a 225nm red shift of its absorption maximum upon the addition of F- in DMSO. D2 also exhibited a fluorescence turn-off response towards the fluoride ion. The emission intensity of D2 decreased drastically along the increasing F- concentration and the detection limit for F- was as low as 3.2×10-9mol/L. 1H NMR and HRMS-ESI results indicated that the formation of NBI-O- through the desilylation reaction of F- with NBI-OSi was responsible for the spectral changes. Overall, this kind of NBI-type molecules represent a new type chemosensor for the spectral detection of fluoride ion in solution.

1-[(6-Chloro-pyridin-3-yl)meth-yl]-10-nitro-1,2,3,5,6,7,8,9-octa-hydro-5,9-methano-imidazo[1,2-a]azocin-5-ol.

In the title compound, C16H19ClN4O3, the cyclo-hexane ring displays a chair formation and the tetra-hydro-pyridine ring displays an envelope conformation with the methyl-ene C atom as the flap; the imidazolidine ring also displays an envelope conformation with a methyl-ene C atom as the flap. In the crystal, O-H⋯N hydrogen bonds between hy-droxy groups and pyridine rings link inversion-related mol-ecules into dimers. Weak C-H⋯O hydrogen bonds further link the dimers into supra-molecular chains running along the c axis.

(E)-1-(2,2-Dimeth-oxy-eth-yl)-2-(nitro-methyl-idene)imidazolidine.

In the title compound, C(8)H(15)N(3)O(4), the 2-(nitro-methyl-ene)imidazolidine fragment is close to being planar (r.m.s. deviation = 0.027 Å), which may be correlated with delocalization of the electrons and the effect of the strongly electron-withdrawing NO(2) group. An intra-molecular N-H⋯O link generates an S(6) ring. The same H atom also forms a weak inter-molecular N-H⋯O hydrogen bond, which results in C(7) chains propagating in [010].

1-[(1,3-Dithio-lan-2-yl)meth-yl]-6-methyl-8-nitro-1,2,3,5,6,7-hexa-hydro-imidazo[1,2-c]pyrimidine.

In the title compound, C(11)H(18)N(4)O(2)S(2), the dithiol-ane ring displays an envelope conformation, the tetra-hydro-pyrimidine ring has a conformation that is between half-chair and screw-boat, and the imidazole ring is essentially planar (r.m.s. deviation = 0.0017 Å). No significant directional inter-molecular inter-actions are present in the structure.

(E)-1-[(1,3-Dioxan-4-yl)meth-yl]-2-(nitro-methyl-idene)imidazolidine.

In the title compound, C(9)H(15)N(3)O(4), the 1,3-dioxane ring displays a chair conformation and the five-membered ring is close to planar (r.m.s. deviation = 0.054 Å). An intra-molecular N-H⋯O hydrogen bond to one of the nitro-group O atoms generates an S(6) ring. In the crystal, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into C(6) chains propagating in [010] and a C-H⋯O link also occurs.

1-[(1,3-Dithio-lan-2-yl)meth-yl]-8-nitro-6-propyl-1,2,3,5,6,7-hexa-hydro-imidazo[1,2-c]pyrimidine.

In the title compound, C(13)H(22)N(4)O(2)S(2), the six-membered ring displays a half-chair conformation. The olefin amine unit is close to being coplanar with the imidazolidine ring (r.m.s. deviation = 0.059 Å). The dithiol-ane ring adopts a twisted conformation. In the crystal, mol-ecules are linked by weak C-H⋯O inter-actions.

1-(2,2-Dimeth-oxy-eth-yl)-8-nitro-1,2,3,5,6,7-hexa-hydro-imidazo[1,2-a]pyridin-5-ol.

In the title compound, C(11)H(19)N(3)O(5), the six-membered ring displays a half-chair conformation and the imidazolidine ring is essentially planar (r.m.s. deviation = 0.088 Å). An inter-molecular hydrogen bond between the hy-droxy O atom and a nitro O atom stabilizes the crystal packing.

1-[(6-Chloro-3-pyrid-yl)meth-yl]-5-eth-oxy-8-nitro-1,2,3,5,6,7-hexa-hydro-imidazo[1,2-a]pyridine.

In the title compound, C(15)H(19)ClN(4)O(3), an active agrochemical possessing insecticidal activity, the dihedral angle between the mean planes passing through the pyridine ring and the five-membered ring is 87.3 (2)°. The fused pyridine ring adopts a twisted sofa conformation. The mol-ecular structure features close intra-molecular C-H⋯N and C-H⋯O hydrogen bonding.

cis-Nitromethylene neonicotinoids as new nicotinic family: synthesis, structural diversity, and insecticidal evaluation of hexahydroimidazo[1,2-alpha]pyridine.

A series of neonicotinoids analogues of hexahydroimidazo[1,2-alpha]pyridine were modified at 5-, 6-, and 7-positions, and their insecticidal activities were evaluated. Introducing a methyl or ethyl at 7-position increased the insecticidal activities, while other substituents decreased activities. When alkyl substituents were introduced to 7-position, the insecticidal activities against Pea aphids decreased in the order methyl (7a)>ethyl (7b)>n-butyl (7e)>phenyl (7f)>n-propyl (7c)>iso-propyl (7d), p-NO(2)-phenyl (7g). Modifications at 5-, 6- or both at 6- and 7-positions with methyl or ethyl were unfavorable to activities. Interestingly, introducing methyl to 7-position not only increased insecticidal activities against pea aphids, but also show higher insecticidal activities than imidacloprid against imidacloprid-resistant brown planthopper.

Synthesis, insecticidal activity, and QSAR of novel nitromethylene neonicotinoids with tetrahydropyridine fixed cis configuration and exo-ring ether modification.

To keep the nitro group in the cis position, a series of nitromethylene neonicotinoids containing a tetrahydropyridine ring with exo-ring ether modifications were designed and synthesized. All of the compounds were characterized and confirmed by 1H NMR, high-resolution mass spectroscopy, elemental analysis, and IR. The bioassay tests showed that some of them exhibited good insecticidal activities against pea aphids. On the basis of 10 nitromethylene derivatives, the quantitative structure-bioactivity relationship (QSAR) was analyzed and established. The results suggested that AlogP98 and Dipole_Mopac might be the important parameters related with biological activities.

Syntheses and biological activities of octahydro-1H-cyclopenta[d]pyrimidine derivatives.

Various nitromethylene derivatives were synthesized regioselectively. Compounds 8a-f were obtained by the reaction of 1-((5-chloropyridin-2-yl)methyl)-2-(nitromethylene)-octahydro-1H-cyclopenta[d]-pyrimidine (3) with primary amines and formaldehyde. The synthesized compounds were identified by 1H NMR, HRMS (EI), and IR, and preliminary bioassays indicated that most of them showed moderate insecticidal activities against Aphis craccivora. The relationship between hydrophobicity and biological activity was also discussed.