FURTHER OXIDATION OF AMINE GROUPS ON DAAF RESULTS IN THE EXTREMELY POWERFUL EXPLOSIVE 3, 3’-DINITROAZOXYFURAZAN. DNAF’S EXPLOSIVE PROPERTIES RATE IT AS ONE OF THE MOSTPOWERFUL OF THE CONVENTIONAL EXPLOSIVES WITH EXCEEDINGLY HIGH VELOCITY OF DETONATION, VERY HIGH HEAT O FORMATION AND GOOD OXYGEN BALANCE. DNAF IS ALSO CASTABLE, MELTING AT 110-112OC AND BOILING AT 270°C [1]. THE LITERATURE METHODS FOR DAAF OXIDATION TO DNAF REQUIRE AMMONIUM PERSULPHATE [2] OR SODIUM PERSULPHATE [2]; WITH HYDROGEN PEROXIDE AND SULPHURIC ACID, YIELD WAS 60%. DNAF CAN ALSO BE FORMED IN BY DIRECT OXIDATION OF 3, 3’-DIAMINO-4, 4’-AZOFURAZAN INTO A 250 ML CONICAL BEAKER WAS ADDED 27.5 G 50% HYDROGEN PEROXIDE DILUTED WITH 17.5 ML WATER. IT WAS THEN CHILLED TO 5OC.30 G AMMONIUM PERSULPHATE WAS THEN DISSOLVED INTO THE PEROXIDE SOLUTION AND LEFT TO COOL IN THE FREEZER. ANOTHER SOLUTION WAS MADE BY DISSOLVING 2.5 G DAAF INTO 32 G 98% SULPHURIC ACID AND WAS SLOWLY ADDED TO THE COOLED PEROXIDE SOLUTION WHILE MAINTAINING THE TEMPERATURE BELOW 20OC. ON ADDITION THE DAAF PRECIPITATED AS A VERY FINE ORANGE SUSPENSION. THE BEAKER WAS THEN PLACED IN AN OIL BATH HEATED TO 40°C AND STIRRED BY USE OF A DRILL PRESS. THIS WAS MAINTAINED FOR 8 HOURS, THE ORANGE SOLUTION TURNING BRIGHT YELLOW. THE SOLUTION WAS THEN DROWNED IN 200 ML ICE COLD WATER AND FILTERED, FLUSHED WITH MORE WATER THEN DISSOLVED INTO 150ML DICHLOROMETHANE, THE DCM SOLUTION WAS THEN WASHED WITH DILUTE SODIUM BICARBONATE/WATER SOLUTION. THE YELLOW DCM SOLUTION WAS THEN SEPARATED AND EVAPORATED TO YIELD YELLOW CRYSTALS OF DNAF. YIELD WAS 1.3 G (40%). THE DNAF WAS PRESSED INTO A DRINKING STRAW, TAPED TO A LEAD BLOCK, BURIED UNDER SAND AND DETONATED.

LINKAGE ISOMERISM IN COORDINATION COMPOUNDS IS DUE TO BINDING OF AN AMBIDENTATE LIGAND (E.G., NO2-NCS-. ETC.) TO A METAL CENTER THROUGH THE ONE OR THE OTHER OF ITS TWO TERMINAL DONOR ATOMS, GIVING RISE TO TWO DIFFERENT COMPLEXES [1]. THE RELATIVE STABILITY OF THE TWO ISOMERS IS ASSOCIATED PRIMARILY WITH THE DONATING TENDENCIES OF THE TWO DONOR ATOMS. MOREOVER, ALSO STERIC EFFECTS CAN PLAY A DETERMINING ROLE, WHEN THE TWO BINDING MODES INVOLVE DIFFERENT STERIC HINDRANCE TOWARD CO-LIGANDS PRESENT IN THE COORDINATION SPHERE [2]. MOST OF THESE SYSTEMS SHOW THERMO CHROMIC FUNCTIONS IN THE SOLID STATE [3]. IN THIS STUDY THE THERMO KINETIC AND THERMODYNAMIC PARAMETERS OF LINKAGE ISOMERIZATION REACTION OF DINITROBIS (ETHYLENEDIAMINE) NICKEL (II) COMPLEX WERE OBTAINED BY MEANS OF DIFFERENTIAL SCANNING CALORIMETRY (DSC). THE DSC CURVES SHOWED THAT THE NITRO ISOMER IS IN A STABLE STATE AT ROOM TEMPERATURE WHICH CAN BE CONVERTED TO A METASTABLE STATE OF NITRITO ISOMER AT ELEVATED TEMPERATURE. IN ADDITION, IN THIS INVESTIGATION A THERMO CHROMIC PHENOMENON ASSOCIATED WITH LINKAGE ISOMERIZATION OF N-BOUNDED NITRO ISOMER TO O-BOUNDED NITRITO ISOMER AT 140-150 OC WAS REPORTED WHICH THIS PHENOMENON WAS REVERSIBLE ON COOLING.

THE NITRITE ION (NO2) IS AN AMBIDENTATE LIGAND THAT CAN BIND TO AMETAL CENTER THROUGH MORE THAN ONE DONOR ATOM, EITHER THE NITROGEN OR THE OXYGEN ATOM, WHICH ARE WELL-KNOWN AS NITRO AND NITRITO LINKAGE ISOMERS, RESPECTIVELY [1]. RECENTLY, A GROWING INTEREST IS ALSO DEVOTED TO STUDY OF PHOTOAND THERMAL-INDUCED INTERCONVERSION OF NOX SPECIES IN THE TRANSITION METAL COMPOUNDS. THE VARIOUS FORMS OF NITROGEN OXIDES MAY COEXIST UNDER NORMAL PHYSIOLOGICAL CONDITIONS WHICH INTERACTIONS OF THESE SPECIES WITH METAL CENTERS, ESSENTIALLY HEME AND NON-HEME IRON ARE DIRECTLY RELATED TO THE NOX BINDING MODES IN THE REACTIVE SPECIES [2]. IN THIS STUDY LINKAGE ISOMERIZATION OF DINITRITO ISOMER OF TRANS-[CO(CYCLAM)(ONO)2]+ (CYCLAM= 1, 4, 8, 11- TETRAAZACYCLOTETRADECANE, [14]ANEN4) WAS FOLLOWED BY UV-VIS SPECTROSCOPY IN SOLUTION. TWO ISOSBESTIC POINTS WERE OBSERVED IN ABSORPTION SPECTRA DURING THERMALLY CONVERSION OF DINITRITO TO DINITRO ISOMERIZATION. IT SEEMS THAT DINITRITO ISOMER COMPLETELY CAN ISOMERIZE TO THE DINITRO ONE THROUGH A TWO-STAGE IRREVERSIBLE PROCESS BY FORMATION AN UNSTABLE NITRO-NITRITO INTERMEDIATE IN FIRST STAGE TO FORM STABLE DINITRO ISOMER IN SECOND STAGE. A MULTIVARIATE CURVE RESOLUTION ALTERNATING LEAST SQUARES (MCRALS) METHOD BASED ON THE HARD-MODELING WAS APPLIED TO RESOLVE THE KINETIC DATA [3]. ALSO, THE PURE SPECTRAL PROFILES COMPONENTS INVOLVED IN LINKAGE ISOMERIZATION PROCESS WERE ELUCIDATED BY SINGULAR VALUE DECOMPOSITION (SVD) AND EVOLVING FACTOR ANALYSIS (EFA). FROM THE SHAPE OF THE CONCENTRATION PROFILES, A THREE CONSECUTIVE FIRST-ORDER KINETIC MODEL WAS SUGGESTED ACCORDING TO SCHEME 1. THE SPECTRAL DATA SHOW A GOOD CORRELATION WITH THOSE RECOVERED BY MCR METHOD.

INTRODUCTION: EXAMPLES OF LINKAGE ISOMERISM OF NITRITE ION IN WHICH NITRO LIGAND MAY COORDINATE THROUGH EITHER ITS NITROGEN OR OXYGEN DONOR ATOM, ARE PREVALENT IN COBALT (III) TETRAAMMINE AND PENTAAMMINE COMPLEXES IN SUCH COMPLEXES, THE NITROGEN-BONDED NITRO ISOMER IS FAVORED THAN THE O-BONDED NITRITO FORM AND LINKAGE ISOMERISM CAN BE INDUCED BY PHOTOCHEMICAL REACTION OR UPON HEATING [1].IN THIS STUDY, LINKAGE ISOMERIZATION OF THE CIS-DINITRITOTETRAMMINECOBALT (III) COMPLEX BY COMPUTATIONAL APPROACH USING DENSITY FUNCTIONAL THEORY (DFT) WAS INVESTIGATED. ASSUMING A TWOSTAGE ISOMERIZATION, THE DINITRITO ISOMER THROUGH THE NITRITO-NITRO INTERMEDIATE ISOMERIZES TO DINITRO FORM. THE GEOMETRY OF THE REACTANT (DINITRITO), INTERMEDIATE (NITRITO-NITRO), PRODUCT (DINITRO) AND ALSO TRANSITION STATES OF THE FIRST (TS1) AND SECOND (TS2) STAGE ISOMERIZATION WAS CHARACTERIZED IN GAS PHASE (SEE BELOW FIGURE). IN ADDITION, THE THERMODYNAMIC AND KINETIC OF THE DINITRITO TO DINITRO ISOMERIZATION WITH THE DOUBLE AIM OF ELUCIDATING THE REACTION MECHANISM WAS INVESTIGATED. IN ORDER TO GAIN FURTHER INSIGHT INTO ELECTRONIC STRUCTURES OF LINKAGE ISOMERS, THE NATURAL POPULATION ANALYSIS METHOD (NPA) WAS PERFORMED.

LINKAGE ISOMERIZATION PHENOMENON IS ONE OF THE MOST IMPORTANT TOPICS IN COORDINATION CHEMISTRY WHICH HAVE BEEN DEVELOPED MORE THAN A CENTURY. WHEN AN AMBIDENTATE LIGAND BINDS TO METAL CENTER THROUGH ONE OF ITS TWO POTENTIAL TERMINAL DONOR ATOMS, GIVING RISE TO TWO DIFFERENT COMPLEXES [1-2]. FOR EXAMPLE, THE ION NITRITE (NO2 –) CAN BIND TO THE METAL CENTER WITH EITHER THE NITROGEN OR OXYGEN ATOMS WHICH ARE CALLED THE NITRO AND NITRITO ISOMERS, RESPECTIVELY. THE RELATIVE STABILITY OF TWO ISOMERS DEPENDS UPON DONATING OF DONOR ATOMS AND THE NATURE OF THE OUTER AND INNER SPHERE COMPLEX [3]. IN THIS INVESTIGATION A QUANTUM MECHANICAL APPROACH WAS EMPLOYED TO ELUCIDATE ELECTRONIC STRUCTURE OF PLAUSIBLE SPECIES OF LINKAGE ISOMERS OF TRANS-DINITRO(1,4,8,11- TETRAAZACYCLOTETRADECANE) COBALT (III) AND TRANS-DINITRITO (1,4,8,11- TETRAAZACYCLOTETRADECANE) COBALT (III) COMPLEXES. ALSO, USING THE OPTIMIZED STRUCTURES OF DINITRO AND DINITRITO ISOMERS, THE INTERMEDIATES AND TRANSITION STATES OF LINKAGE ISOMERIZATION REACTION WERE DETERMINED. A DENSITY FUNCTIONAL THEORY (DFT) WAS CARRIED OUT BY GAUSSIAN 2009 PACKAGE USING B3LYP FUNCTIONS AND 6-31G+(D,P) BASIS SET THAT ADDED A P-TYPE AND D-TYPE POLARIZATION FUNCTION TO HYDROGEN AND HEAVIER ATOMS. ALL THE MOLECULAR STRUCTURES WERE FULLY OPTIMIZED IN GAS PHASE USING THE QUASI-RELATIVISTIC EFFECTIVE CORE POTENTIAL (ECPS) FOR COBALT. IN ADDITION, THE THERMODYNAMIC AND THERMO KINETIC DATA OF ISOMERIZATION WAS EVALUATED BY THE COMPUTATIONAL METHODS.

THE EXPLORATION OF COORDINATION MODES OF NITROGEN OXIDE DERIVATIVES (NOX) TO TRANSITIONAL METAL CENTERS SUCH AS HEME, HAS CONTINUALLY INCREASED OWING TO THE RECOGNITION OF THE ROLE OF THESE SPECIES IN THE CHEMISTRY AND BIOCHEMISTRY FIELDS [1].THE NITRITO (-ONO)/ NITRO (-NO2) LINKAGE ISOMERIZATION IN POLYAMMINE COMPLEXES OF CO (III) IS AMONG THE MOST WIDELY STUDIED SOLUTION AND SOLID STATE REACTIONS IN COORDINATION CHEMISTRY. LINKAGE ISOMERIZATION OF DINITRITO TO DINITRO ISOMER OF TRANS-BIS (ETHYLENEDIAMINE) COBALT (III) WERE PREVIOUSLY STUDIED IN SOLUTION BY MEANS OF UV-VIS SPECTROMETRY [2] AND IN SOLID STATE USING DIFFERENTIAL SCANNING CALORIMETRY (DSC) [3]. THE RESULTS SHOW THAT THE DINITRITO ISOMER CAN BE CONVERTED TO DINITRO ONES THROUGH A TWO-STAGE PROCESS BY FORMATION OF AN UNSTABLE NITRO-NITRITO INTERMEDIATE WHICH SUBSEQUENTLY CAN CONVERT TO THE STABLE DINITRO ISOMER. IN THIS STUDY, LINKAGE ISOMERIZATION OF THE TRANS-[CO(EN)2(ONO)2]+ (EN=ETHYLENEDIAMINE) WAS INVESTIGATED BY DENSITY FUNCTIONAL THEORY (DFT) USING GAUSSIAN 09 PROGRAM PACKAGE[4]. BY ASSUMING THAT THE DINITRITO ISOMER THROUGH THE NITRITO-NITRO INTERMEDIATE ISOMERIZES TO DINITRO FORM, THE GEOMETRY OF THE REACTANT (DINITRITO), INTERMEDIATE (NITRITO-NITRO), PRODUCT (DINITRO) WERE CHARACTERIZED IN THE GAS PHASE (FIGURE 1). ALSO,THE STRUCTURE OF THE STEPWISE TRANSITION STATES WAS OBTAINED BY THE SYNCHRONOUS TRANSIT-GUIDED QUASI-NEWTON (STQN) METHOD TO ELUCIDATE THE KINETIC AND MECHANISM OF ISOMERIZATION PROCESS. A TIME-DEPENDENT DENSITY FUNCTIONAL THEORY (TD-DFT) CALCULATIONS WERE CARRIED OUT AT B3LYP/6-31+G(D,P) LEVEL IN ORDER TO EVALUATE THE ELECTRONIC SPECTRUM IN THE SINGLET EXCITED STATE WITH POLARIZED CONTINUUM MODEL (PCM).