Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1998-04-22
2001-04-03
Kight, John (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C546S155000, C546S156000, C546S196000, C546S269100, C546S282700, C548S525000, C549S060000, C549S389000
Reexamination Certificate
active
06211374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compounds displaying photochromic behavior and more particularly to water soluble photochromic compounds of the type comprising a pyran ring which is closed in a ground state and open in an excited state. The present invention also relates to methods for preparing these compounds.
BACKGROUND OF THE INVENTION
Photochromic compounds are compounds which can reversibly change color and/or degree of light transmission when they are exposed to a source of exciting electromagnetic radiation, e.g., visible light or ultraviolet light most commonly. The compounds return to their original state of color and/or light transmission when the exposure source is removed and/or the compound is exposed to counteracting light. Many forms of photochromic compounds are known. For example, U.S. Pat. Nos. 3,100,778; 3,501,410; 4,220,708; 4,882,438; 5,532,361; and 5,543,533 describe a variety of photochromic structures.
One class of photochromic compounds are pyran-based in that these compounds incorporate a pyran moiety. Color changes in such compounds result from configurational changes in the pyran moiety. In one form corresponding to the ground state, the pyran moiety is closed and forms a six membered ring. Pyran-based photochromic compounds in the ground state are most commonly colorless. In another form corresponding to the excited state, exposure to light causes the pyran ring to open up. Pyran-based photochromic compounds in the excited, open state exhibit a second state of color. For example, some of the previously known pyran-based photochromic compounds display yellow, yellow-orange, or blue colors when in the excited configuration.
The closed configuration is generally more stable than the open configuration. Accordingly, in the absence of an exciting source of radiation, pyran-based compounds in the open state tend to revert back to the closed configuration. To help stabilize the open configuration, the pyran moiety is typically linked to moieties having extended &pgr;-electronic systems. These stabilizing moieties are linked to the pyran ring in such a way that at least one such stabilizing moiety is linked to one side of the open pyran ring, and at least one other is linked to the other side of the open pyran ring. Examples of such compounds are known and have been described in U.S. Pat. Nos. 3,100,778; 3,501,410; 5,532,361; and 5,543,533.
Stability of pyran-based photochromic compounds still remains a concern, however. Many of the pyran-based compounds fade from a colored state to a colorless state too quickly. In other materials, a lack of stability is evidenced by weak colors. There is a need, therefore, for pyran-based photochromic compounds having greater stability and that display more vibrant, pure colors.
Temperature dependence is another concern. Many pyran-based photochromic compounds display photochromic properties only at temperatures well above or below ambient conditions. It would be desirable if such compounds could display photochromism over a wide temperature range, including ambient temperatures.
Many of the previously known photochromic compounds also lack water solubility, preventing their use in aqueous systems. Still others are made by reaction schemes having low yields, affecting the efficiency and economics of manufacture.
SUMMARY OF THE INVENTION
The present invention provides pyran-based photochromic compounds characterized by improved stability when in an open, excited configuration. As a consequence, photochromic compounds of the present invention display extremely vibrant, stable colors which can be red, pink, purple, orange, or the like depending upon how the principles of the invention are implemented. The photochromic compounds of the invention also are substantially water soluble, making them suitable for use in aqueous systems if desired. Additionally, photochromic compounds of this invention exhibit photochromism over a wide temperature range, including ambient temperatures. As still yet another advantage, the photochromic compounds of this invention can be made according to reaction schemes characterized by very high yields.
The advantages of the present invention are provided, at least in part, by functionalizing a pyran-based photochromic compound with carboxylate functionality in such a way that the carboxylate has sufficient mobility to engage in intermolecular and intramolecular interactions. In preferred embodiments, such a mobile carboxylate provided on one side of an open pyran ring is preferably capable of complexing with functionality on the other side of the open pyran ring, greatly stabilizing the open configuration.
In one aspect, the advantages of the present invention are achieved by an ionic photochromic compound, comprising:
(a) a pyran moiety comprising oxygen as a ring constituent;
(b) an aromatic moiety comprising an aromatic ring fused to the pyran moiety;
(c) at least one heterocyclic ring moiety linked to the pyran moiety at an ortho position relative to the oxygen ring constituent; and
(d) at least one carboxylate moiety linked to the heterocyclic ring moiety.
In another aspect, the present invention provides a method of making an ionic photochromic compound, comprising the steps of:
(a) providing a reactant comprising a heterocyclic ring including a nitrogen atom as a ring constituent and comprising an aromatic moiety having an aromatic ring fused to the heterocyclic ring;
(b) attaching a carboxyl moiety to the nitrogen atom in a manner such that the carboxyl moiety is linked to the nitrogen atom by a divalent linking group;
(c) providing an aromatic reactant comprising an aromatic ring having substituents reactive with the product of step (b) to form a reaction product comprising a pyran ring having an oxygen atom as a ring substituent and a saturated carbon atom ortho to the oxygen atom, said substituents being reactive such that the aromatic ring of the aromatic ring is fused to the resultant pyran ring and the saturated carbon atom of the pyran ring ortho to the oxygen atom is linked to the heterocyclic ring; and
(d) reacting the product of step (b) with the aromatic reactant under conditions effective to form said pyran ring, whereby the ionic photochromic compound is formed.
REFERENCES:
patent: 3100778 (1963-08-01), Berman
patent: 3501410 (1970-03-01), Newland et al.
patent: 4220708 (1980-09-01), Heller
patent: 4225661 (1980-09-01), Muzyczko
patent: 4882438 (1989-11-01), Tanaka et al.
patent: 5532361 (1996-07-01), Allegrini et al.
patent: 5543533 (1996-08-01), Allegrini et al.
Chemical Abstract vol. 110 No. 85.587, Omote et al. “Spiropyran Photochromic Material and Its Coloration”, 1988.*
Abrahart, “Dyes and Their Intermediates”, 1968, Pergamon Press p. 8.*
Intelligent Gels—Using solvent-swollen polymer networks that respond to stimuli, scientists are beginning to develop a soft, wet, organic technology; By: Ron Dagani; Dated: Jun. 9, 1997 C&EN; pp. 26-37.
Fujimura et al, Chemical Abstract vol. 112 No. 129229, “Thermochromic Recording Materials” Mar. 7, 1988.*
Arai et al, Chemical Abstract vol. 124 No. 215776, “Prep. of Photochromic Spiropyrans Linked to Methyl Cellulose & Photoregulation” 1996.
Covington Raymond
Faegre & Benson LLP
Kight John
LandOfFree
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