The present invention is generally directed to dimeric and polymeric fluorescent or colored dyes having rigid spacing groups, and methods for their preparation and use in various analytical methods. Description of the Related Art Fluorescent and/or colored dyes are known to be particularly suitable for applications in which a highly sensitive detection reagent is desirable. Dyes that are able to preferentially label a specific ingredient or component in a sample enable the researcher to determine the presence, quantity and/or location of that specific ingredient or component. In addition, specific systems can be monitored with respect to their spatial and temporal distribution in diverse environments. Fluorescence and colorimetric methods are extremely widespread in chemistry and biology. These methods give useful information on the presence, structure, distance, orientation, complexation and/or location for biomolecules. In addition, time-resolved methods are increasingly used in measurements of dynamics and kinetics. As a result, many strategies for fluorescence or color labeling of biomolecules, such as nucleic acids and protein, have been developed. Since analysis of biomolecules typically occurs in an aqueous environment, the focus has been on development and use of water soluble dyes. Highly fluorescent or colored dyes are desirable since use of such dyes increases the signal to noise ratio and provides other related benefits. Accordingly, attempts have been made to increase the signal from known fluorescent and/or colored moieties. For example, dimeric and polymeric compounds comprising two or more fluorescent and/or colored moieties have been prepared in anticipation that such compounds would result in brighter dyes. However, as a result of intramolecular fluorescence quenching, the known dimeric and polymeric dyes have not achieved the desired increase in brightness. There is thus a need in the art for water soluble dyes having an increased molar brightness. Ideally, such dyes and biomarkers should be intensely colored or fluorescent and should be available in a variety of colors and fluorescent wavelengths. The present invention fulfills this need and provides further related advantages. BRIEF SUMMARY In brief, embodiments of the present invention are generally directed to compounds useful as water soluble, fluorescent and/or colored dyes and/or probes that enable visual detection of analyte molecules, such as biomolecules, as well as reagents for their preparation. Methods for visually detecting analyte molecules using the dyes are also described. Embodiments of the presently disclosed dyes include two or more fluorescent and/or colored moieties covalently linked by a linker ("L4"). In contrast to previous reports of dimeric and/or polymeric dyes, the present dyes are significantly brighter than the corresponding monomeric dye compound. While, not wishing to be bound by theory, it is believed that the linker moiety provides sufficient spatial separation between the fluorescent and/or colored moieties such that intramolecular fluorescence quenching is reduced and/or eliminated. The water soluble, fluorescent or colored dyes of embodiments of the invention are intensely colored and/or fluorescent and can be readily observed by visual inspection or other means. In some embodiments the compounds may be observed without prior illumination or chemical or enzymatic activation. By appropriate selection of the dye, as described herein, visually detectable analyte molecules of a variety of colors may be obtained, In one embodiment, compounds having the following structure (I) are provided: or a stereoisomer, tautomer or salt thereof, wherein R1, R2, R3, R4, R5, L1, L2, L3, L4, M, m and n are as defined herein. Compounds of structure (I) find utility in a number of applications, including use as fluorescent and/or colored dyes in various analytical methods. In another embodiment, a method for staining a sample is provided, the method comprises adding to said sample a compound of structure (I) in an amount sufficient to produce an optical response when said sample is illuminated at an appropriate wavelength. In still other embodiments, the present disclosure provides a method for visually detecting an analyte molecule, comprising: (a) providing a compound of (I); and (b) detecting the compound by its visible properties. Other disclosed methods include a method for visually detecting a biomolecule, the method comprising: (a) admixing a compound of structure (I) with one or more biomolecules; and (b) detecting the compound by its visible properties. Other embodiments provide a method for visually detecting an analyte, the method comprising: (a) providing a compound as disclosed herein, wherein R2 or R3 comprises a linker comprising a covalent bond to a targeting moiety having specificity for the analyte; (b) admixing the compound and the analyte, thereby associating the targeting moiety and the analyte; and (c) detecting the compound by its visible properties. Other embodiments are directed to a composition comprising a compound of structure (I) and one or more analyte molecule, such as a biomolecule. Use of such compositions in analytical methods for detection of the one or more biomolecules is also provided. In some other different embodiments is provided a compound of structure (II): (II) or a stereoisomer, salt or tautomer thereof, wherein R1, R2, R3, R4, R5, Lla, L2, L3, L4, G, m and n are as defined herein. Compounds of structure (II) find utility in a number of applications, including use as intermediates for preparation of fluorescent and/or colored dyes of structure (I). In yet other embodiments a method for labeling an analyte molecule is provided, the method comprising: (a) admixing a compound of structure (II), wherein R2 or R3 is Q or a linker comprising a covalent bond to Q, with the analyte molecule; (b) forming a conjugate of the compound and the analyte molecule; and (c) reacting the conjugate with a compound of formula M-Llb-G', thereby forming at least one covalent bond by reaction of G and G', wherein R2, R3, Q, G and M-Llb-G' are as defined herein. In some different embodiments another method for labeling an analyte molecule is provided, the method comprising: (a) admixing a compound of structure (II), wherein R2 or R3 is Q or a linker comprising a covalent bond to Q, with a compound of formula M-Llb-G', thereby forming at least one covalent bond by reaction of G and G'; and (b) reacting the product of step (A) with the analyte molecule, thereby forming a conjugate of the product of step (A) and the analyte molecule wherein R2, R3, Q, G and M-Llb-G' are as defined herein. In more different embodiments, a method for preparing a compound of structure (I) is provided, the method comprising admixing a compound of structure (II) with a compound of formula M-Llb-G', thereby forming at least one covalent bond by reaction of G and G', wherein G and M-Llb-G' are as defined herein. Still more embodiments are directed to a fluorescent compound comprising Y fluorescent moieties M, wherein the fluorescent compound has a peak fluorescence emission upon excitation with a predetermined wavelength of ultraviolet light of at least 85% of Y times greater than the peak fluorescence emission of a single M moiety upon excitation with the same wavelength of ultraviolet light, and wherein Y is an integer of 2 or more. These and other aspects of the invention will be apparent upon reference to the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS In the figures, identical reference numbers identify similar elements. The sizes and relative positions of elements in the figures are not necessarily drawn to scale and some of these elements are arbitrarily enlarged and positioned to improve figure legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the figures. FIG. 1 provides UV absorbance spectra for representative compounds comprising a triethylene glycol spacer and a comparative compound at 5 μιη and pH 9. FIG. 2 is UV absorbance data for representative compounds comprising a hexaethylene glycol spacer and a comparative compound at 5 μιη and pH 9. FIG. 3 is fluorescence emission spectra for representative compounds comprising a triethylene glycol spacer and a comparative compound at 50 nM and pH 9. FIG. 4 presents fluorescence emission spectra for representative compounds comprising a hexaethylene glycol spacer and a comparative compound at 50 nM and pH 9. FIG. 5 is UV absorbance data at 5 μιη for representative compounds comprising four hexaethylene glycol spacers and two or three fluorescein moieties relative to a comparative compound having a single fluorescein moiety. FIG. 6 is a graph of fluorescent emission data at 5 μιη for representative compounds comprising four hexaethylene glycol spacers and two or three fluorescein moieties relative to a comparative compound having a single fluorescein moiety. FIG. 7 shows comparative fluorescence emission response for illustrative compounds with various m values. FIG. 8 provides data comparing fluorescence emission for the "HEG" compound, wherein m is 1, 2 or 3, relative to Compound A. FIG. 9 provides UV absorbance data for compound 1-32, compound 1-46 and Compound B. FIG. 10 shows the results of a reaction trimerizing compound 1-42 as analyzed by PAGE. FIG. 11 provides data comparing the fluorescence signal of seven compounds in a dead and necrotic cell population. FIG. 12 shows fluorescence intensity of an antibody conjugate of 1-51 versus an antibody conjugate of Compound G. FIG. 13 shows comparisons of an 1-51 conjugation and a Compound G reference antibody. FIG. 14 shows a comparison of UCHTl-I-51, UCHT1-BB515, and UCHT1-FITC. FIG. 15 shows expression levels of CD3 compared to a MEF standard curve. FIG. 16 shows a comparison of UCHTl-I-16 fractions to FITC. FIG. 17 shows a comparison of UCHT 1-1-16 fractions to 1-56 conjugates. FIG. 18 shows a comparison of the UCHT 1-1-51 -like analogue, UCHT1 1-16, with UCHT1 1-56 (lOx), and UCHT1 1-53 (6x). FIG. 19 provides data comparing the UCHT1 1-51 -like analogue, UCHT1 1-16, was compared with UCHT1 1-56 (lOx), and UCHT1 1-53 (6x). FIG. 20 shows the results of a regression analysis performed on data produced when testing UCHT1 1-16 and UCHT1 1-49 conjugates to demonstrate equivalency between conjugations. FIG. 21 A shows correlations between 1-16 and 1-45 as determined using regression analysis. FIG. 2 IB shows titration curve overlays and compared to references. FIG. 21C shows example qualitative data showing background FL and cell morphology comparing Compound D and 1-45. FIG. 22 shows affinity curves, as histograms, with compound emission detected in the FL1-A channel. FIG. 23 A shows comparisons of fluorescence intensity of off target, non-specific binding of UCHT 1-1-2 IB, UCHTl-I-16, and reference, UCHT1-FITC, and FIG. 23B presents supporting data. FIG. 24 presents results of a regression analysis that was applied to the data to review correlations and relative affinities. FIG. 25, shows signal to noise data for UCHT1-I-21B, UCHTl-I-51, and UCHT1-FITC. FIGs. 26 A and 26B provide data comparing UCHT1 Compound G AND UCHT1 1-51 in a plasma interference study using PBMC. FIG. 26A shows data resulting from the addition of 0% glycine, and FIG. 26B shows data resulting from the addition of 2.5% glycine. DETAILED DESCRIPTION In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. Unless the context requires otherwise, throughout the present specification and claims, the word "comprise" and variations thereof, such as, "comprises" and "comprising" are to be construed in an open, inclusive sense, that is, as "including, but not limited to". Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. "Amino" refers to the - H2 group. "Carboxy" refers to the -C02H group. "Cyano" refers to the -CN group. "Formyl" refers to the -C(=0)H group. "Hydroxy" or "hydroxyl" refers to the -OH group. "Imino" refers to the = H group. "Nitro" refers to the -N02 group. "Oxo" refers to the =0 substituent group. "Sulfhydryl" refers to the -SH group. "Thioxo" refers to the =S group. "Alkyl" refers to a straight or branched hydrocarbon chain group consisting solely of carbon and hydrogen atoms, containing no unsaturation, having from one to twelve carbon atoms (Ci-Ci2 alkyl), one to eight carbon atoms (Ci-C8 alkyl) or one to six carbon atoms (Ci-C6 alkyl), and which is attached to the rest of the molecule by a single bond, e.g., methyl, ethyl, ^-propyl, 1-methylethyl (z'so-propyl), «-butyl, «-pentyl, 1, 1-dimethylethyl (t-butyl), 3-methylhexyl, 2-methylhexyl, and the like. Unless stated otherwise specifically in the specification, alkyl groups are optionally substituted. "Alkylene" or "alkylene chain" refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing no unsaturation, and having from one to twelve carbon atoms, e.g., methylene, ethylene, propylene, «-butylene, ethenylene, propenylene, «-butenylene, propynylene, «-butynylene, and the like. The alkylene chain is attached to the rest of the molecule through a single bond and to the radical group through a single bond. The points of attachment of the alkylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkylene is optionally substituted. "Alkenylene" or "alkenylene chain" refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon double bond and having from two to twelve carbon atoms, e.g., ethenylene, propenylene, «-butenylene, and the like. The alkenylene chain is attached to the rest of the molecule through a single bond and to the radical group through a double bond or a single bond. The points of attachment of the alkenylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkenylene is optionally substituted. "Alkynylene" or "alkynylene chain" refers to a straight or branched divalent hydrocarbon chain linking the rest of the molecule to a radical group, consisting solely of carbon and hydrogen, containing at least one carbon-carbon triple bond and having from two to twelve carbon atoms, e.g., ethenylene, propenylene, «-butenylene, and the like. The alkynylene chain is attached to the rest of the molecule through a single bond and to the radical group through a double bond or a single bond. The points of attachment of the alkynylene chain to the rest of the molecule and to the radical group can be through one carbon or any two carbons within the chain. Unless stated otherwise specifically in the specification, alkynylene is optionally substituted. "Alkylether" refers to any alkyl group as defined above, wherein at least one carbon-carbon bond is replaced with a carbon-oxygen bond. The carbon-oxygen bond may be on the terminal end (as in an alkoxy group) or the carbon oxygen bond may be internal (i.e., C-O-C). Alkylethers include at least one carbon oxygen bond, but may include more than one. For example, polyethylene glycol (PEG) is included within the meaning of alkylether. Unless stated otherwise specifically in the specification, an alkylether group is optionally substituted. For example, in some embodiments an alkylether is substituted with an alcohol or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Alkoxy" refers to a group of the formula -ORa where Ra is an alkyl group as defined above containing one to twelve carbon atoms. Unless stated otherwise specifically in the specification, an alkoxy group is optionally substituted. "Alkoxyalkylether" refers to a group of the formula -ORaRb where Ra is an alkylene group as defined above containing one to twelve carbon atoms, and Rb is an alkylether group as defined herein. Unless stated otherwise specifically in the specification, an alkoxyalkylether group is optionally substituted, for example substituted with an alcohol or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Heteroalkyl" refers to an alkyl group, as defined above, comprising at least one heteroatom (e.g., N, O, P or S) within the alkyl group or at a terminus of the alkyl group. In some embodiments, the heteroatom is within the alkyl group (i.e., the heteroalkyl comprises at least one carbon-[heteroatom]x-carbon bond, where x is 1, 2 or 3). In other embodiments, the heteroatom is at a terminus of the alkyl group and thus serves to join the alkyl group to the remainder of the molecule (e.g., Ml-H-A), where Ml is a portion of the molecule, H is a heteroatom and A is an alkyl group). Unless stated otherwise specifically in the specification, a heteroalkyl group is optionally substituted. Exemplary heteroalkyl groups include ethylene oxide (e.g., polyethylene oxide), optionally including phosphorous-oxygen bonds, such as phosphodiester bonds. "Heteroalkoxy" refers to a group of the formula -ORa where Ra is a heteroalkyl group as defined above containing one to twelve carbon atoms. Unless stated otherwise specifically in the specification, a heteroalkoxy group is optionally substituted. "Heteroalkylene" refers to an alkylene group, as defined above, comprising at least one heteroatom (e.g., N, O, P or S) within the alkylene chain or at a terminus of the alkylene chain. In some embodiments, the heteroatom is within the alkylene chain (i.e., the heteroalkylene comprises at least one carbon-[heteroatom]-carbon bond, where x is 1, 2 or 3). In other embodiments, the heteroatom is at a terminus of the alkylene and thus serves to join the alkylene to the remainder of the molecule (e.g., M1-H-A-M2, where Ml and M2 are portions of the molecule, H is a heteroatom and A is an alkylene). Unless stated otherwise specifically in the specification, a heteroalkylene group is optionally substituted. Exemplary heteroalkylene groups include ethylene oxide (e.g., polyethylene oxide) and the "C" linking group illustrated below: "C linker" Multimers of the above C-linker are included in various embodiments of heteroalkylene linkers. "Heteroalkenylene" is a heteroalkylene, as defined above, comprising at least one carbon-carbon double bond. Unless stated otherwise specifically in the specification, a heteroalkenylene group is optionally substituted. "Heteroalkynylene" is a heteroalkylene comprising at least one carbon-carbon triple bond. Unless stated otherwise specifically in the specification, a heteroalkynylene group is optionally substituted. "Heteroatomic" in reference to a "heteroatomic linker" refers to a linker group consisting of one or more heteroatoms. Exemplary heteroatomic linkers include single atoms selected from the group consisting of O, N, P and S, and multiple heteroatoms for example a linker having the formula -P(0")(=0)0- or -OP(0")(=0)0-and multimers and combinations thereof. "Phosphate" refers to the -OP(=0)(Ra)R group, wherein Ra is OH, O" or ORc; and Rb is OH, O", ORc, a thiophosphate group or a further phosphate group, wherein Rc is a counter ion (e.g., Na+ and the like). "Phosphoalkyl" refers to the -OP(=0)(Ra)Rb group, wherein Ra is OH, O" or ORc; and Rb is -Oalkyl, wherein Rc is a counter ion (e.g., Na+ and the like). Unless stated otherwise specifically in the specification, a phosphoalkyl group is optionally substituted. For example, in certain embodiments, the -Oalkyl moiety in a phosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether, thiophosphoalkylether or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Phosphoalkylether" refers to the -OP(=0)(Ra)Rb group, wherein Ra is OH, O" or ORc; and Rb is -Oalkylether, wherein Rc is a counter ion (e.g., Na+ and the like). Unless stated otherwise specifically in the specification, a phosphoalkylether group is optionally substituted. For example, in certain embodiments, the -Oalkylether moiety in a phosphoalkylether group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether, thiophosphoalkylether or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Thiophosphate" refers to the -OP(=Ra)(Rb)Rc group, wherein Ra is O or S, Rb is OH, O", S", ORd or SRd; and Rc is OH, SH, O", S", ORd, SRd, a phosphate group or a further thiophosphate group, wherein Rd is a counter ion (e.g., Na+ and the like) and provided that: i) Ra is S; ii) Rb is S" or SRd; iii)Rc is SH, S" or SRd; or iv) a combination of i), ii) and/or iii). "Thiophosphoalkyl" refers to the -OP(=Ra)(Rb)Rc group, wherein Ra is O or S, Rb is OH, O", S", ORd or SRd; and Rc is -Oalkyl, wherein Rd is a counter ion (e.g., Na+ and the like) and provided that: i) Ra is S; ii) Rb is S" or SRd; or iii)Ra is S and Rb is S" or SRd. Unless stated otherwise specifically in the specification, a thiophosphoalkyl group is optionally substituted. For example, in certain embodiments, the -Oalkyl moiety in a thiophosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether, thiophosphoalkylether or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Thiophosphoalkylether" refers to the -OP(=Ra)(Rb)Rc group, wherein Ra is O or S, Rb is OH, O", S", ORd or SR¾ and Rc is -Oalkylether, wherein Rd is a counter ion (e.g., Na+ and the like) and provided that: i) Ra is S; ii) ¾ is S" or SR^; or iii)Ra is S and ¾ is S" or SRd. Unless stated otherwise specifically in the specification, a thiophosphoalkylether group is optionally substituted. For example, in certain embodiments, the -Oalkylether moiety in a thiophosphoalkyl group is optionally substituted with one or more of hydroxyl, amino, sulfhydryl, phosphate, thiophosphate, phosphoalkyl, thiophosphoalkyl, phosphoalkylether, thiophosphoalkylether or -OP(=Ra)(Rb)Rc, wherein each of Ra, Rb and Rc is as defined for compounds of structure (I). "Carbocyclic" refers to a stable 3- to 18-membered aromatic or non-aromatic ring comprising 3 to 18 carbon atoms. Unless stated otherwise specifically in the specification, a carbocyclic ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems, and may be partially or fully saturated. Non-aromatic carbocyclyl radicals include cycloalkyl, while aromatic carbocyclyl radicals include aryl. Unless stated otherwise specifically in the specification, a carbocyclic group is optionally substituted. "Cycloalkyl" refers to a stable non-aromatic monocyclic or polycyclic carbocyclic ring, which may include fused or bridged ring systems, having from three to fifteen carbon atoms, preferably having from three to ten carbon atoms, and which is saturated or unsaturated and attached to the rest of the molecule by a single bond. Monocyclic cyclocalkyls include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptly, and cyclooctyl. Polycyclic cycloalkyls include, for example, adamantyl, norbornyl, decalinyl, 7,7-dimethyl-bicyclo-[2.2.1]heptanyl, and the like. Unless stated otherwise specifically in the specification, a cycloalkyl group is optionally substituted. "Aryl" refers to a ring system comprising at least one carbocyclic aromatic ring. In some embodiments, an aryl comprises from 6 to 18 carbon atoms. The aryl ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems. Aryls include, but are not limited to, aryls derived from aceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene, benzene, chrysene, fluoranthene, fluorene, as-indacene, s-indacene, indane, indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene, and triphenylene. Unless stated otherwise specifically in the specification, an aryl group is optionally substituted. "Heterocyclic" refers to a stable 3- to 18-membered aromatic or non-aromatic ring comprising one to twelve carbon atoms and from one to six heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur. Unless stated otherwise specifically in the specification, the heterocyclic ring may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems; and the nitrogen, carbon or sulfur atoms in the heterocyclic ring may be optionally oxidized; the nitrogen atom may be optionally quatemized; and the heterocyclic ring may be partially or fully saturated. Examples of aromatic heterocyclic rings are listed below in the definition of heteroaryls (i.e., heteroaryl being a subset of heterocyclic). Examples of non-aromatic heterocyclic rings include, but are not limited to, dioxolanyl, thienyl[l,3]dithianyl, decahydroisoquinolyl, imidazolinyl, imidazolidinyl, isothiazolidinyl, isoxazolidinyl, morpholinyl, octahydroindolyl, octahydroisoindolyl, 2-oxopiperazinyl, 2-oxopiperidinyl, 2-oxopyrrolidinyl, oxazolidinyl, piperidinyl, piperazinyl, 4-piperidonyl, pyrrolidinyl, pyrazolidinyl, pyrazolopyrimidinyl, quinuclidinyl, thiazolidinyl, tetrahydrofuryl, trioxanyl, trithianyl, triazinanyl, tetrahydropyranyl, thiomorpholinyl, thiamorpholinyl, 1-oxo-thiomorpholinyl, and 1, 1-dioxo-thiomorpholinyl. Unless stated otherwise specifically in the specification, a heterocyclic group is optionally substituted. "Heteroaryl" refers to a 5- to 14-membered ring system comprising one to thirteen carbon atoms, one to six heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur, and at least one aromatic ring. For purposes of certain embodiments of this invention, the heteroaryl radical may be a monocyclic, bicyclic, tricyclic or tetracyclic ring system, which may include fused or bridged ring systems; and the nitrogen, carbon or sulfur atoms in the heteroaryl radical may be optionally oxidized; the nitrogen atom may be optionally quatemized. Examples include, but are not limited to, azepinyl, acridinyl, benzimidazolyl, benzthiazolyl, benzindolyl, benzodioxolyl, benzofuranyl, benzooxazolyl, benzothiazolyl, benzothiadiazolyl, benzo[£][l,4]dioxepinyl, 1,4-benzodioxanyl, benzonaphthofuranyl, benzoxazolyl, benzodioxolyl, benzodioxinyl, benzopyranyl, benzopyranonyl, benzofuranyl, benzofuranonyl, benzothienyl (benzothiophenyl), benzotriazolyl, benzo[4,6]imidazo[l,2-a]pyridinyl, benzoxazolinonyl, benzimidazolthionyl, carbazolyl, cinnolinyl, dibenzofuranyl, dibenzothiophenyl, furanyl, furanonyl, isothiazolyl, imidazolyl, indazolyl, indolyl, indazolyl, isoindolyl, indolinyl, isoindolinyl, isoquinolyl, indolizinyl, isoxazolyl, naphthyridinyl, oxadiazolyl, 2-oxoazepinyl, oxazolyl, oxiranyl, 1-oxidopyridinyl, 1-oxidopyrimidinyl, 1-oxidopyrazinyl, 1-oxidopyridazinyl, 1 -phenyl- lH-pyrrolyl, phenazinyl, phenothiazinyl, phenoxazinyl, phthalazinyl, pteridinyl, pteridinonyl, purinyl, pyrrolyl, pyrazolyl, pyridinyl, pyridinonyl, pyrazinyl, pyrimidinyl, pryrimidinonyl, pyridazinyl, pyrrolyl, pyrido[2,3-