Browsing by Author "Chandrasekharan, K."

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?(3) measurements and optical limiting in dibenzylideneacetone and its derivatives
(2006) Kiran, A.J.; Chandrasekharan, K.; Nooji, S.R.; Shashikala, H.D.; Umesh, G.; Kalluraya, B.
We investigated the third order nonlinear optical properties of dibenzylidene acetone (1,5-diphenyl-1, 4-pentadeine-3-one) and its derivatives. The nonlinear measurements were performed by using single beam Z-scan technique with Q-switched Nd:YAG nanosecond laser pulses at 532 nm. Open aperture data for dibenzylidene and its derivatives demonstrate the presence of two-photon absorption at this wavelength. The dependence of ?(3) on donor/acceptor type substituents to the basic compound clearly shows the electronic origin of nonlinearity and hence demonstrates that the mechanism by which the third order nonlinear response enhanced is not by the thermal effects, but instead due to the strong nonlinear absorption and nonlinear refraction of the compounds. The derivatives of the basic compound show very good optical limiting behavior. � 2005 Elsevier B.V. All rights reserved.
?(3) measurements and optical limiting in dibenzylideneacetone and its derivatives
(2006) Kiran, A.J.; Chandrasekharan, K.; Nooji, S.R.; Shashikala, H.D.; Umesh, G.; Kalluraya, B.
We investigated the third order nonlinear optical properties of dibenzylidene acetone (1,5-diphenyl-1, 4-pentadeine-3-one) and its derivatives. The nonlinear measurements were performed by using single beam Z-scan technique with Q-switched Nd:YAG nanosecond laser pulses at 532 nm. Open aperture data for dibenzylidene and its derivatives demonstrate the presence of two-photon absorption at this wavelength. The dependence of ?(3) on donor/acceptor type substituents to the basic compound clearly shows the electronic origin of nonlinearity and hence demonstrates that the mechanism by which the third order nonlinear response enhanced is not by the thermal effects, but instead due to the strong nonlinear absorption and nonlinear refraction of the compounds. The derivatives of the basic compound show very good optical limiting behavior. © 2005 Elsevier B.V. All rights reserved.
An investigation on photophysical and third–order nonlinear optical properties of novel thermally–stable thiophene–imidazo [2,1-b][1,3,4] thiadiazole based azomethines
(Elsevier Ltd, 2019) Kakekochi, V.; Udayakumar, U.; Nikhil, N.P.; Chandrasekharan, K.
The use of ?–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto–electronic properties. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1–TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1–TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z–scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (?eff) of the order of 10?10 m W?1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the ?–conjugation, providing an improved ?eff (0.81 × 10?10 m W?1) to TI1 compared to that of TI2 (0.55 × 10?10 m W?1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices. © 2019 Elsevier Ltd
Butterfly-Shaped Thiophene-Pyridine Hybrids: Green Electroluminescence and Large Third-Order Optical Nonlinearities
(Wiley-VCH Verlag info@wiley-vch.de, 2020) Kakekochi, V.; Gangadharappa, S.C.; Nikhil, P.P.; Chandrasekharan, K.; Darshan, V.; Narayanan Unni, K.N.; Udayakumar, U.K.
A set of four symmetric, butterfly-shaped 4-(4-(decyloxy)phenyl)-2,6-di(thiophen-2-yl)pyridine (TPY) derivatives 2TPA-TPY (TPY center and triphenylamine end groups), 2CBZ-TPY (TPY center and N-ethyl carbazole end groups), 2TPY-TPA (triphenylamine center and TPY at the periphery) and 2TPY-CBZ (N-ethyl carbazole center and TPY at the periphery) was synthesized. The molecules show reverse saturable absorption (RSA) which is consistent with two-photon absorption (2PA) associated with excited-state absorption (ESA) when excited using a 532 nm laser beam. The molecules 2TPA-TPY and 2TPY-TPA possess extremely low limiting thresholds of 1.73 and 2.68 J cm?2, respectively. An organic light-emitting diode (OLED) fabricated from 2TPA-TPY exhibits green emission with a maximum luminance of 207 cd m?2, a current efficiency (?CE) of 1.51cd A?1, a maximum power efficiency (?Pmax) of 0.46 lm W?1 and an external quantum efficiency (?EQE) of 0.48 % at 100 cd m?2. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chalcones: Possible new materials for third-order nonlinear optics
(Nova Science Publishers, Inc., 2011) Kiran, A.J.; Chandrasekharan, K.; Kalluraya, B.; Shashikala, H.D.
'Search for potential materials' for third-order nonlinear optics has been of continuing interest in recent years. In this context, organic molecules are increasingly being recognized as the materials of the future because their molecular nature combined with the versatility of synthetic chemistry can be used to alter and optimize molecular structure to maximize third order nonlinear response. Chalcones have received considerable interest as materials for second-order nonlinear optical applications due to their ability to crystallize in noncentrosymmetric structure and their blue light transmittance. Being charge transfer compounds, chalcones can also possess large thirdorder nonlinearities due to their π-conjugated structure. In this article, we discuss the structure-nonlinear response relationship among a few chalcones and the possibility of using them for third-order applications. A meager or no work, to our knowledge, has been done so far on these molecules in this regard. Z-scan and degenerate four-wave mixing techniques were employed to investigate third-order optical nonlinearities of chalcone derivatives. Some of these molecules possess large χ (3) of magnitude as high as 10-12 esu and exhibit strong optical limiting properties. Possible mechanisms that are responsible for optical limiting property of these molecules have been discussed. . © 2011 by Nova Science Publishers, Inc. All rights reserved.
D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties
(2016) Prashanth, Kumar, K.R.; Udayakumar, D.; Siji, Narendran, N.K.; Chandrasekharan, K.; Srivastava, R.
In this communication, we report synthesis and characterization of new D-A conjugated polymers (P1-P3) consisting of electron-donating (D) 3,4-didodecyloxythiophene, electron-accepting (A) 1,3,4-oxadiazole unit and non-conjugation linkers. The conjugated segment in P1-P3 contains only five aromatic rings resulting in short conjugation length, but has an alternate D-A arrangement which significantly enhances the intramolecular charge transfer (ICT) interaction within the segment. As a result, these polymers exhibited low optical band gap in the range 2.51 2.76 eV. Fluorescence emission studies revealed that the polymer thin films emit intense blue light with emission maxima in the wavelength rage 430 480 nm. All three polymers undergo both oxidation and reduction processes under electrochemical conditions. Further, these polymers (P1 P3) exhibit low-lying HOMO and LUMO levels as a result of D-A structure of the conjugated segment. Polymer light-emitting devices were fabricated using these polymers as emissive layer with a device configuration of ITO/MoO 3/polymer/LiF/Al. The test device based on P2 emitted blue light with a low threshold voltage of 5 V. Z-scan studies reveal that the polymers exhibit a strong optical limiting behavior. The value of the nonlinear absorption coefficient (?) of polymers is of the order 10 ?11m/W which indicates that these materials may be accomplished for fabricating optical limiters. [Figure not available: see fulltext.] 2016, Indian Academy of Sciences.
D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties
(Springer India sanjiv.goswami@springer.co.in, 2016) Prashanth Kumar, K.R.; Udayakumar, D.; Siji Narendran, N.K.; Chandrasekharan, K.; Srivastava, R.
In this communication, we report synthesis and characterization of new D-A conjugated polymers (P1-P3) consisting of electron-donating (D) 3,4-didodecyloxythiophene, electron-accepting (A) 1,3,4-oxadiazole unit and non-conjugation linkers. The conjugated segment in P1-P3 contains only five aromatic rings resulting in short conjugation length, but has an alternate D-A arrangement which significantly enhances the intramolecular charge transfer (ICT) interaction within the segment. As a result, these polymers exhibited low optical band gap in the range 2.51–2.76 eV. Fluorescence emission studies revealed that the polymer thin films emit intense blue light with emission maxima in the wavelength rage 430–480 nm. All three polymers undergo both oxidation and reduction processes under electrochemical conditions. Further, these polymers (P1–P3) exhibit low-lying HOMO and LUMO levels as a result of D-A structure of the conjugated segment. Polymer light-emitting devices were fabricated using these polymers as emissive layer with a device configuration of ITO/MoO 3/polymer/LiF/Al. The test device based on P2 emitted blue light with a low threshold voltage of 5 V. Z-scan studies reveal that the polymers exhibit a strong optical limiting behavior. The value of the nonlinear absorption coefficient (?) of polymers is of the order 10 ?11m/W which indicates that these materials may be accomplished for fabricating optical limiters. [Figure not available: see fulltext.] © 2016, Indian Academy of Sciences.
Effects of substituents on the enrichment of the optical limiting action of novel imidazo[2,1-: B] [1,3,4]thiadiazole fused thiophene-based small molecules
(2019) Kakekochi, V.; Udayakumar, D.; Nikhil, P.P.; Chandrasekharan, K.
The imidazo[2,1-b][1,3,4]thiadiazole (ITD) ring is a fused, planar aromatic heterocyclic system consisting of four heteroatoms with a bridgehead nitrogen atom. In this study, three new donor-acceptor-donor (D-A-D)-type organic molecules (ThITD1-ThITD3) were designed and synthesized, wherein ITD was an electron acceptor unit and the thiophene/phenyl moieties were electron donor units that produced a D-A-D configuration. The thiophene-ITD core structure comprises three different groups viz., thiophene-2-acetonitrile (ThITD1), phenylacetonitrile (ThITD2) and rhodanine-3-acetic acid (ThITD3), and the effect of substituents on the optical and electrochemical properties have been discussed based on structural modifications. The third-order nonlinear optical (NLO) properties analyzed by the Z-scan technique reveal that the molecules exhibit effective two photon absorption (TPA) with ThITD3 possessing substantially higher effective TPA coefficient (?eff) than ThITD1 and ThITD2, which is comparable to the reported ?eff values. The results unravel that ITD as an acceptor with an appropriate ?-linker will be a promising candidate for application in the field of optoelectronics/photonics. Herein, the thiophene-ITD ring system was explored for NLO applications and reported for the first time. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Effects of substituents on the enrichment of the optical limiting action of novel imidazo[2,1-: B] [1,3,4]thiadiazole fused thiophene-based small molecules
(Royal Society of Chemistry, 2019) Kakekochi, V.; Udayakumar, D.; Nikhil, P.P.; Chandrasekharan, K.
The imidazo[2,1-b][1,3,4]thiadiazole (ITD) ring is a fused, planar aromatic heterocyclic system consisting of four heteroatoms with a bridgehead nitrogen atom. In this study, three new donor-acceptor-donor (D-A-D)-type organic molecules (ThITD1-ThITD3) were designed and synthesized, wherein ITD was an electron acceptor unit and the thiophene/phenyl moieties were electron donor units that produced a D-A-D configuration. The thiophene-ITD core structure comprises three different groups viz., thiophene-2-acetonitrile (ThITD1), phenylacetonitrile (ThITD2) and rhodanine-3-acetic acid (ThITD3), and the effect of substituents on the optical and electrochemical properties have been discussed based on structural modifications. The third-order nonlinear optical (NLO) properties analyzed by the Z-scan technique reveal that the molecules exhibit effective two photon absorption (TPA) with ThITD3 possessing substantially higher effective TPA coefficient (?eff) than ThITD1 and ThITD2, which is comparable to the reported ?eff values. The results unravel that ITD as an acceptor with an appropriate ?-linker will be a promising candidate for application in the field of optoelectronics/photonics. Herein, the thiophene-ITD ring system was explored for NLO applications and reported for the first time. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Facile synthesis and exploration of excited state assisted two-photon absorption properties of D-A-D type thiophene-pyridine derivatives
(Royal Society of Chemistry, 2020) Kakekochi, V.; Chatnahalli Gangadharappa, S.; Nikhil, P.P.; Chandrasekharan, K.; Wolcan, E.; Udayakumar, U.K.
A series of trigonal-shaped molecules (TPyT and TPyP) and a polymer (P2TPy) with donor-acceptor-donor (D-A-D) structural arrangement were designed with thiophene and 2,4,6-trisubstituted pyridine as the backbone i.e., a 4-(4-(decyloxy)phenyl)-2,6-di(thiophen-2-yl)pyridine core structure, for the first time and synthesized via a microwave assisted one pot reaction. The extension of conjugation of the system by substituting thiophene acrylonitrile (TPyT) and phenyl acrylonitriles (TPyP and P2TPy) via low cost condensation reactions improved the linear optical, electronic and thermal properties of the synthesized compounds. Furthermore, the nonlinear absorption (NLA) was also enriched appreciably by increasing the conjugation. The three compounds showed an "effective two-photon absorption" phenomenon with the NLA coefficient (?eff) of the order of 10-10 m W-1. The suitability to be utilized in the fabrication of all-optical limiting devices is best achieved by polymer P2TPy as it exhibits substantially higher ?eff (7.02 × 10-10 m W-1) and an extremely low optical limiting threshold (1.42 J cm-2). © 2020 The Royal Society of Chemistry and Owner Societies.
Impact of donor acceptor alternation on optical power limiting behavior of H Shaped thiophene imidazo[2,1-b] [1,3,4]thiadiazole flanked conjugated oligomers
(2020) Kakekochi, V.; Nikhil, P, P.; Chandrasekharan, K.; Udayakumar, D.
A new series of four D A D configured conjugated oligomers with H type structure, possessing two thiophene imidazo [2,1-b][1,3,4]thiadiazole branches and thiophene (TIT), thiophene 1,3,4-oxadiazole thiophene (TITO), thiazolo [5,4-d]thiazole (TITz), phenyl thiazolo [5,4-d]thiazole phenyl (TIPTz) units as central core moieties were efficiently synthesized. These core moieties were specifically selected to increase the planarity, rigidity, stability, extend the ? conjugation and to understand the influence of central core on nonlinear absorption coefficient (?eff) and optical limiting behavior of the synthesized oligomers. The structure-property relationships of these oligomers were established by the optical absorption (UV Vis), electrochemical (CV) and theoretical (DFT) studies. The effective two photon absorption of oligomers was confirmed by single beam Z scan analysis. The exceptional increase in nonlinear response was achieved with the oligomers TITO and TIPTz with nonlinear absorption coefficient (?eff) of 1.62 and 2.71 10?10 m W?1, and limiting thresholds of 6.02 and 3.14 J cm?2, respectively, which suggest that these oligomers could be potent materials for practical applications in laser photonics. 2020 Elsevier Ltd
Impact of donor–acceptor alternation on optical power limiting behavior of H–Shaped thiophene–imidazo[2,1-b] [1,3,4]thiadiazole flanked conjugated oligomers
(Elsevier Ltd, 2020) Kakekochi, V.; Nikhil, P.; Chandrasekharan, K.; Udayakumar, U.
A new series of four D–A–D configured conjugated oligomers with H–type structure, possessing two thiophene–imidazo [2,1-b][1,3,4]thiadiazole branches and thiophene (TIT), thiophene–1,3,4-oxadiazole–thiophene (TITO), thiazolo [5,4-d]thiazole (TITz), phenyl–thiazolo [5,4-d]thiazole–phenyl (TIPTz) units as central core moieties were efficiently synthesized. These core moieties were specifically selected to increase the planarity, rigidity, stability, extend the ?–conjugation and to understand the influence of central core on nonlinear absorption coefficient (?eff) and optical limiting behavior of the synthesized oligomers. The structure-property relationships of these oligomers were established by the optical absorption (UV–Vis), electrochemical (CV) and theoretical (DFT) studies. The “effective two–photon absorption” of oligomers was confirmed by single–beam Z–scan analysis. The exceptional increase in nonlinear response was achieved with the oligomers TITO and TIPTz with nonlinear absorption coefficient (?eff) of 1.62 and 2.71 × 10?10 m W?1, and limiting thresholds of 6.02 and 3.14 J cm?2, respectively, which suggest that these oligomers could be potent materials for practical applications in laser photonics. © 2020 Elsevier Ltd
An investigation on photophysical and third order nonlinear optical properties of novel thermally stable thiophene imidazo [2,1-b][1,3,4] thiadiazole based azomethines
(2019) Kakekochi, V.; Udayakumar, D.; P, N.P.; Chandrasekharan, K.
The use of ? conjugated semiconducting materials in flexible and large area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto electronic properties. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1 TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1 TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (?eff) of the order of 10?10 m W?1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the ? conjugation, providing an improved ?eff (0.81 10?10 m W?1) to TI1 compared to that of TI2 (0.55 10?10 m W?1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices. 2019 Elsevier Ltd
Nonlinear optical properties of p-(N,N-dimethylamino)dibenzylideneacetone doped polymer
(2008) Kiran, A.J.; Satheesh, Rai, N.; Udayakumar, D.; Chandrasekharan, K.; Kalluraya, B.; Philip, R.; Shashikala, H.D.; Adhikari, A.V.
A bis-chalcone derivative, p-(N,N-dimethylamino) dibenzylideneacetone was synthesized. Its third-order nonlinear susceptibility was determined to be as high as 10-12 esu by employing single beam Z-scan and degenerate four wave mixing techniques using Nd:YAG 7 ns laser pulses at 532 nm. The compound was doped in to poly(methylmethacrylate) matrix and the third-order nonlinearity was investigated by using Z-scan technique. The nonlinear refractive index of the doped polymer is found to be negative, and its magnitude is of the order of 10-10 esu. The results show that the compound exhibits strong reverse saturable absorption and a good optical limiting property and hence may be used as a promising dopant material. The study on concentration dependence of nonlinear optical parameters has been presented. 2007 Elsevier Ltd. All rights reserved.
Nonlinear optical properties of p-(N,N-dimethylamino)dibenzylideneacetone doped polymer
(2008) Kiran, A.J.; Satheesh Rai, N.; Udayakumar, D.; Chandrasekharan, K.; Kalluraya, B.; Philip, R.; Shashikala, H.D.; Vasudeva Adhikari, A.V.
A bis-chalcone derivative, p-(N,N-dimethylamino) dibenzylideneacetone was synthesized. Its third-order nonlinear susceptibility was determined to be as high as 10-12 esu by employing single beam Z-scan and degenerate four wave mixing techniques using Nd:YAG 7 ns laser pulses at 532 nm. The compound was doped in to poly(methylmethacrylate) matrix and the third-order nonlinearity was investigated by using Z-scan technique. The nonlinear refractive index of the doped polymer is found to be negative, and its magnitude is of the order of 10-10 esu. The results show that the compound exhibits strong reverse saturable absorption and a good optical limiting property and hence may be used as a promising dopant material. The study on concentration dependence of nonlinear optical parameters has been presented. © 2007 Elsevier Ltd. All rights reserved.
Nonlinear optical studies of 1-3-diaryl-propenones containing 4-methylthiophenyl moieties
(2007) John, Kiran, A.; Mithun, A.; Shivarama, Holla, B.; Shashikala, H.D.; Umesh, G.; Chandrasekharan, K.
The third-order nonlinear optical properties of chalcone derivatives have been studied using the single beam Z-scan technique. The dependence of ?(3) on different donor and acceptor type substituents demonstrates the electronic nonlinearity of compounds. The largest value of nonlinear refractive index, n2, measured for a high electron donor substituted molecule is -2.033 10-11 esu. These molecules exhibit a strong two-photon absorption and interesting optical limiting of nanosecond laser pulses at 532 nm. 2006 Elsevier B.V. All rights reserved.
Nonlinear optical studies of 1-3-diaryl-propenones containing 4-methylthiophenyl moieties
(2007) John Kiran, A.; Mithun, A.; Shivarama Holla, B.; Shashikala, H.D.; Umesh, G.; Chandrasekharan, K.
The third-order nonlinear optical properties of chalcone derivatives have been studied using the single beam Z-scan technique. The dependence of ?(3) on different donor and acceptor type substituents demonstrates the electronic nonlinearity of compounds. The largest value of nonlinear refractive index, n2, measured for a high electron donor substituted molecule is -2.033 × 10-11 esu. These molecules exhibit a strong two-photon absorption and interesting optical limiting of nanosecond laser pulses at 532 nm. © 2006 Elsevier B.V. All rights reserved.
Nonlinear optical studies of a newly synthesized copolymer containing oxadiazole and substituted thiophenes
(2007) John, Kiran, A.; Udayakumar, D.; Chandrasekharan, K.; Ahdikari, A.V.; Shashikala, H.D.; Philip, R.
We investigated the third-order nonlinear optical properties of a newly synthesized soluble copolymer containing oxadiazole and thiophene units using Z-scan and Degenerate Four Wave Mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of ?(3) determined from both experiments. Z-scan results indicate a negative nonlinear refractive index, n2, whose magnitude is of the order of 10-10 esu. The copolymer exhibits strong nonlinear absorption and good optical limiting properties at 532 nm, and hence may be a potential material for optical limiting applications. 2006 Elsevier B.V. All rights reserved.
Nonlinear optical studies of a newly synthesized copolymer containing oxadiazole and substituted thiophenes
(2007) John Kiran, A.; Udayakumar, D.; Chandrasekharan, K.; Ahdikari, A.V.; Shashikala, H.D.; Philip, R.
We investigated the third-order nonlinear optical properties of a newly synthesized soluble copolymer containing oxadiazole and thiophene units using Z-scan and Degenerate Four Wave Mixing (DFWM) techniques. The measurements were performed at 532 nm with 7 ns pulses from a Nd:YAG laser. We found a good agreement between the values of ?(3) determined from both experiments. Z-scan results indicate a negative nonlinear refractive index, n2, whose magnitude is of the order of 10-10 esu. The copolymer exhibits strong nonlinear absorption and good optical limiting properties at 532 nm, and hence may be a potential material for optical limiting applications. © 2006 Elsevier B.V. All rights reserved.
Radioprotection by copper and zinc complexes of 5-aminosalicylic acid: A preliminary study
(2008) Mantena, S.K.; Unnikrishnan, M.K.; Chandrasekharan, K.
The effect of copper and zinc complexes of 5-aminosalicylic acid (hereafter referred to as Cu-5ASA and Zn-5ASA, respectively) against whole-body gamma radiation-induced cytotoxicity was studied in Swiss albino mice. Protection against lethal irradiation was evaluated from 30 day mouse survival (10 Gy) and endogenous spleen colony assay (11 Gy); and against sublethal dose (4 Gy) was assessed from gamma irradiation (RT)-induced formation of micronuclei in the mouse bone marrow 24 h postirradiation. Pretreatment with either Cu-5ASA (2.5-9 mg/kg) or Zn-5ASA (3.5-14 mg/kg) intraperitoneally (i.p.) delayed and reduced percentage mortality in mice exposed to 10 Gy RT. The doses 9 mg/kg for Cu-5ASA and 7 mg/kg for Zn-5ASA were found to be the most effective dose in preventing RT-induced weight loss and reducing percentage mortality. Both the drugs also caused an increase in the endogenous spleen colonies in mouse exposed to 11 Gy RT. At sublethal doses of RT, pretreatment with either Cu-5ASA or Zn-5ASA resulted in a significant decrease in the RT-induced micronucleated polychromatic erythrocytes and normochromatic erythrocytes (MPCEs and MNCEs) and an increase in the ratio of PCE to NCE (P/N), at 24 h postirradiation. These results show that both Cu-5ASA and Zn-5ASA are effective in protecting normal tissues against lethal and sublethal doses of RT. Further pretreatment with either Cu-5ASA or Zn-5ASA enhanced the survival of tumor-bearing mice (Ehrlich's ascites carcinoma) exposed to 7.5 Gy RT. In fact, both the complexes caused an increase in the mean and average survival times (MST and AST) when compared to the irradiated control, suggesting a synergetic effect of these drugs with radiation in causing cytotoxicity to the tumor cells. The data clearly indicate that both Cu-5ASA and Zn-5ASA significantly reduced the deleterious effect of radiation and hence could be useful agents in reducing the side effects of therapeutic radiation. 2008 by Begell House, Inc.