Colormetric sensor compositions and methods

Details Colormetric sensor compositions and methods Colormetric sensor compositions and methods

2000-05-26

2002-11-19

Shah, Mukund J. (Department: 1624)

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitrogen attached directly or indirectly to the purine ring...

C544S344000, C544S353000, C544S354000, C544S355000, C544S356000

Reexamination Certificate

active

06482949

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to compositions and methods for binding and optically sensing anions, cations, and neutral species. Analytical methods for such species is the primary goal of optical sensing. These methods may be qualitative or quantitative. In particular, compositions containing pyrroles as the key recognition element and a quinoxaline backbone as part of the compound, are shown to provide a system with a built-in optical probe for selective sensing.
2. Description of Related Art
In the recent decades, supramolecular chemists have devoted considerable effort to developing systems capable of recognizing, sensing, and transporting anions (Dietrich, et al., 1997). This is an area of effort that is considered both timely and important. Indeed, some 70 to 75% of all natural biological processes are thought to involve a negatively charged species (Schmidtchen, 1988).
Anion recognition constitutes an important problem area within the generalized field of supramolecular chemistry. Not surprisingly, therefore, it has been pursued extensively, particularly within the calixarene domain. Indeed, most attention has focused on calixarene systems that have been modified, via attachment to, or reaction with, electron deficient metal centers, so as to make more electrophilic the normally &pgr;-electron rich calixarene moiety.
Anions constitute key components in food stuffs (e.g., fluoride, citrate and benzoate) and are products for, and pollutants from, modern agriculture (e.g., phosphate and nitrate) and can also act as potent toxins (e.g. cyanide). One anion, pertechnetate, is critical to radio-diagnostic and therapy procedures and, in a different isotopic form, is a major radioactive pollutant. Given these few examples, it is clearly important that we have a means to readily monitor the presence of these species in our everyday environment.
Among the range of biologically important anions, fluoride is of particular interest due to its established role in preventing dental caries (Kirk, 1991). Fluoride anion is also being explored extensively as a treatment for osteoporosis, (Riggs, 1984 and Kleerekoper, 1998) and, on a less salubrious level, can lead to fluorosis, (Wiseman, 1970 and Gale, et al., 1996) a type of fluoride toxicity that generally manifests itself clinically in terms of increasing bone density. This diversity of function, both beneficial and otherwise, makes the problem of fluoride anion detection one of considerable current interest. Thus, while traditional methods of fluoride anion analysis, involving, e.g., ion selective electrodes and
19
F-NMR spectroscopy remain important, there is an increasing incentive to find alternative means of analysis, including those based on the use of specific chemosensors. Particularly useful would be systems that can recognize fluoride anion in solution and signal its presence via an easy-to-detect optical signature.
In the past few years, a wide range of anion sensors have been proposed (sapphyrins, Sessler, et al. 1997; calixpyrroles, Gale, et al. 1996 and Sessler, et al., 1998; cyclic polyamines, Dietrich, et al., 1981; Hoseini and Lehn, 1988) guanidinium (Dietrich, et al., 1981 and Metzger, et al., 1997)) that present varying degrees of affinity (and selectivity) toward anions such as F
−
, Cl
−
, H
2
PO
4
−
and/or carboxylates. Unfortunately, and in spite of considerable effort, a need for good anion sensors remains. The number of anion sensors which can select for one biological anion over a range of anions present in vivo (phosphate, chloride, fluoride, etc.) remains at best, very limited. While there exists small molecule sensors which can bind anions relatively well, they do so with little or no specificity. This is particularly true in the case of fluoride anion where few, if any, easy-to-use signaling agents exist.
In addition to anion sensing, it is also desirable to develop sensing elements capable of sensing cations and neutral species. The presence or absence, as well as the level of, various neutral molecular species is a useful diagnostic tool that can signal chemical decomposition. One example is the sensing of cis-3-hexenal (or chemical derivatives thereof), a metabolite of the bacterial
E. Coli
, Salmonela, and Lysteria. Such sensors would find applicability in the food industry as detectors of food contamination and spoilage. They could, for instance, be incorporated into food packaging materials.
Therefore, a need exists to develop methods and compositions for the selective detection of anions, cations, and neutral species in general, and for fluoride in particular. A motivation for the preparation of new sensors is to obtain sensor compounds designed to recognize selectively a particular analyte within a range of species and produce an easily detected signal.
SUMMARY OF THE INVENTION
The present invention provides novel compounds containing both pyrrole-derived anion and neutral species recognition subunits and an aromatic core as the optical or visual signaling group to provide chemosensors that allow for the convenient, color-based sensing of anions. Most commonly, the aromatic core will be a quinoxaline moiety, but may be any aryl system having two pyrroles covalently bound to neighboring (but not necessarily directly ajacent) carbons on an aryl moiety through a C—C single bond connecting pyrroles and the aromatic moiety.
Formula I illustrates the general pyrrole-aryl systems (&agr;,&agr; and &bgr;,&bgr; substitution on the pyrrole rings) along with the specific pyrrole-quinoxaline analog shown directly below. Note that the pyrrole substitution may also be mixed, i.e, &agr;,&bgr; or &bgr;,&agr;. As used herein, “aryl” means any aromatic system consisting of one or more rings which may be homonuclear or heteronuclear, and which may or may not contain aromatic or non-aromatic side groups (substitution), and which may be further complexed to one or more metals. The present invention further provides methods of use and synthetic schemes for these novel compounds.
The present invention provides novel compounds exemplified by the pyrrolic nitrogens used as anion recognition elements with an aromatic core as a signal group. The compounds of the present invention are termed pyrrole-aryls, and as used herein, the compounds of the present invention which, at least, combine these two elements will be referred to as such. Although not shown above, the pyrrole carbon atoms may also be substituted. The aryls may or may not contain heteroatoms. Subsituents may include, but are not limited to, hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide, ester, acyl, or carboxy and may be the same or different at each occurrence.
Compounds of the present invention may be prepared by a condensation between a 1,2-diamine and a 2,3-dipyrryl ethanedione as shown in Scheme 1.
While specific substituents are listed above, the quinoxaline analogs may have a wider variability of substituent groups. R
1
and R
2
may be, individually at each occurrence, hydrogen, alkyl, hydroxyalkyl, glycol, polyglycol, amino, nitro, halo, cyano, aryl, heteroaryl, thio, thioalkyl, amide, ester, acyl, or carboxy. Although not shown above, any or all of these possible substitutions may be present on the remaining available carbon atoms of the quinoxaline. Additionally, any or all of these same possible substitution combinations may also be present on the &agr; or &bgr; positions, or on both the &agr; and &bgr; positions (relative to nitrogen) of the pyrrole rings.
Oxalyl chloride, o-phenylenediamine, 4-nitro-1,2-diaminobenzene were purchased from Aldrich and used without further purification. 4,5-Diamino-1,2-dimethoxybenzene was prepared according to the method of Sessler, 1992. 4,5-Dinitro-1,2-diaminobenzene was prepared according to the method of Cheeseman, 1962.
Thus, in a second respect, the present invention is the 2,3-dipyrryl-ethanediones used to produce the pyrrole-aryls. In this aspect of the inventio

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