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By Larry G. Twidwell, Corby G. Anderson, Camille M. Fleuriault

"The selective precipitation of iron as ammonium jarosite is a well-established industrial technology in base metals hydrometallurgy. It is a key technology in minimizing iron tenors which would be disruptive to downstream processing. It also provides a more readily filterable iron solid to better facilitate materials handling. This paper elucidates the fundamentals behind industrial iron precipitation. Then, the details of the successful optimization of an industrial ammonium jarosite circuit are presented.HYDROMETALLURGICAL IRON REMOVAL FUNDAMENTALS Iron is the fourth most abundant element in the Earth’s crust (5% by weight) and is often found in complex ores such as sulphide-bearing formations. Iron represents an issue though during leaching, a technology which is widely used for the treatment of this type of ore: •,Iron has the particularity of forming hydroxides when leached under certain conditions. Iron hydroxides form a viscous gel, which is difficult to filter and traps valuable elements such as silver. •,Iron is solubilized along with other metals and interferes with the subsequent extraction steps. As a result, purification of the pregnant leach solutions is required to achieve economical extraction of base metals. In the 1960s, metallurgists developed iron precipitation processes for solution purification (Habashi, 1999). Nowadays, precipitation of iron bearing species, such as goethite, hematite or jarosite, has become one of the most common methods used in the industry to purify leach liquors. To be suitable, the precipitate has to be readily filterable and thus must not be too fine of particle size. Precipitation can take place in autoclaves at medium to high temperatures, under an oxygen or air overpressure (Tourre, 1984, Fleuriault 2016, Fleuriault Anderson Shuey, 2016))."

Jan 1, 2016

By M. B. McClenaghan

"The Matheson area of northeastern Ontario is of great interest for mineral exploration because of its geological similarities with the adjacent Timmins, Kirkland Lake and Larder Lake gold camps. Exploration in the area, however, is hampered by the presence of an extensive and thick cover of glacial sediments. For this reason, till geochemistry has become an important exploration method. The Ontario Geological Survey&apos;s Black River-Matheson (BRiM) reconnaissance till sampling project, carried out between 1984 and 1988, was designed to aid exploration in the Matheson area by documenting the Quaternary stratigraphy and providing a database of till geochemistry. Till samples were collected by backhoe trenching of surface pits in areas of thin drift (< 5 m) and by sonic overburden drilling in areas of thicker drift. This paper summarizes the results from the shallow till sampling component of the BRiM project.Two hundred and eighty-two surface samples were collected from Matheson Till, the youngest till sheet in the area, which was deposited during the Late Wisconsinan. For each sample, the non-magnetic heavy mineral (> 3.3 S.G.) and fine (- 250 mesh) till fractions were analyzed geochemically. In addition, visible gold grains were recovered by panning the heavy mineral fraction. Five areas that display multi-element anomalies in both till fractions warrant further investigation: (1) western Egan Township, overlying the Bradley Lake Syenite; (2) around and south of the Munro and Croesus mines, in Munro and Guibord townships; (3) central Garrison Township overlying the Garrison Stock; (4) south of Ore Car Lake in northern Thackeray Township; and (5) southeastern Harker Township. In these areas, Matheson Till has a local provenance and the bedrock sources for these anomalies are nearby in the up-ice (north northwest) direction. Due to the fine-grained nature of gold in bedrock deposits in the BRiM area, the small size of most gold grains recovered from till samples (< 50 um) and the variable distribution of gold in the heavy mineral concentrate and fine fractions, the fine fraction in addition to the more commonly used heavy mineral concentrate should be used for gold exploration.Surface till samples have been affected by weathering to a depth of = 3 m. Weathered till is characterized by a very low carbonate content in the matrix fraction, the absence of sulfide grains in the heavy mineral concentrate and higher concentrations of copper, nickel and zinc in the fine fraction than in the heavy mineral concentrate. As a result of the weathered/ oxidized nature of the surface till samples, the fine fraction is a better sampling medium for base metal exploration."

Jan 1, 1992

By Staff

"The Weyburn Oil Field, located 80 miles southeast of Regina, Saskatchewan, was discovered by Central-Del Rio Oils Limited, in January, 1955. As of January 1st, 1959, the field had 357 wells capable of producing an estimated total of 45,100 barrels of oil per day.Highly portable, economical, drilling rigs are used to penetrate the pay at a depth of 4,400 to 5,100 feet. Presently, the complete drilling operation for an average field well, including drilling, coring, testing, and running casing, requires 12 days. Drilling procedures are conventional for a field of this depth and no serious problems exist. Central-Del Rio core the productive section of all their wells, which provides valuable information for well completions and reservoir studies. Production casing procedure is to set through the zone and perforate the productive inter-val. This was found advisable due to the lensing nature of the porosity and permeability throughout the reservoir, and to the high connate water saturation encountered in the tighter sections of the reservoir in the north and northeast areas of the field.Although a few wells in the field have produced naturally by flowing or pumping without acid treatment, it has generally been necessary to acidize the wells to make them commercial producers. To date, acid treatments appear to effect better stimulation of the limestone reservoir than fracturing treatments. Perforation sealing balls have been used as an aid in selectively treating all of the perforated interval.The majority of the field is on pump, producing at a low gas-oil ratio. The main part of the field has water-free production, with most of the water being produced in the north and northeastern area. Salt-water disposal is now available in the field through two disposal wells completed in the Basal Blairmore sand.The Midale Beds ""Marly"" and ""Vuggy"" zones form the principal reservoir, which is a stratigraphic trap, with the north and northeast edges terminated by a porosity and permeability pinch-out and the south-west and west edges bounded by water-laden porosity. There is no evidence to date of a gas cap. The reservoir apparently is producing on a fluid-expansion-type mechanism. The increasing water production in wells on the southwest and west edges of the field indicated water encroachment from these directions, and suggests some recovery energy may be available from this source.The total probable ultimate remaining recoverable reserves have been estimated at° 332,469,000 barrels of oil. Markets have not been able to keep up with the rate of development of the medium crude re-serves. However, it is felt strongly that substantial additional markets for Weyburn medium crude will be developed by the producers in the near future at realistic wellhead prices."

Jan 1, 1959

By C. Bourgoin

"The factors constraining productivity in the mining of narrow vein ore deposits are numerous and often interdependent. This paper concerns mining techniques capable of reducing some of these constraints in the case of vein deposits whose dip is less than 45 degrees. Modifications of conventional mining methods as well as suggested new developments are presented, as are matters pertaining to the mechanization of operations as a mean of increasing both productivity and work safety. IntroductionThe mining of vein deposits, whose width (thickness) is generally less than 2 metres and whose dip is often variable, calls for the use of varying stoping procedures as well as appropriate infrastructure and equipment. In the case of intermediate dips (15 degrees to 45 degrees), it is generally conceded that the degree of mechanization is limited and that ore removal via gravity is impossible. This paper proposes certain innovations in matters of equipment use and stoping methods, together with certain technical data pertaining to the application of these new procedures Stoping MethodsTo mine vein deposits, one must choose a method that can adapt to irregular ore limits and allow, as well, for good ore recovery with as little dilution as possible. In addition, it is important to minimize development work in waste rock. In principle, one selects a method that is both safe and profitable; this method will be defined mainly by the nature of the vein deposit and its dip, by the competency of the rock formations and by certain technical considerations. Moreover, the stoping procedure in a given deposit may well change with time as a function of new layouts or new equipment."

Jan 1, 1994

By W. G. Spencer, E. Sulis, P. M. Tiley

"Dome Mine&apos;s No.8 shaft is located about 1 km northeast of Dome&apos;s No.3 shaft and mill complex in South Porcupine, Ontario.No.8 shaft was brought into production in 1984 to hoist ore and waste for the complete mine as well as to service the mine from the 1600 level and below. Access above 1600 level is provided by No. 3 shaft.The rectangular shaft has six compartments consisting of two skips, a cage, counterweight, manway, and a service compartment. The over-all size of the shaft is 14 ft 7 in. by 20 ft by 7 in. (Fig. 1). A 7th compartment for shaft deepening is incorporated in the bottom 500 ft of shaft. The shaft is 5470 ft deep. The loading pocket is located at 5300 ft and the dump 61 ft below the collar.Surface facilities consist of a concrete headframe and a structural steel hoistroom which houses the cage and production hoists . The service hoist is a 12-ft diameter double drum, with one 1750 HP DC motor, and the production hoist is a 15-ft diameter double drum with twin 1750 HP DC motors.Both hoists have a single clutch and a single reduction gear train built by Orenstein & Koppel, and equipped with Canadian General Electric drives. The cage hoist is equipped with a disc pinion brake.The skips were originally aluminum 14-ton capacity, Rolla-chute design with steel liners on three sides and 4 in. of rubber on the back, to absorb the loading impact. The original guide rollers consisted of fixed 10 in. pneumatic tires. The face-to-face units were eventually replaced with larger airplane-type tires mounted on a spring loaded pivot arm."

Jan 1, 1993

By W. F. MacIsaac

"The large low-grade Copper Mountain deposit is located in the northern portion of the Gaspé Cooper Mines property. It is approximately 1 mile north of the Needle Mountain deposit. The orebody outlined to date lies in the top 1,000 feet of the Grande Greve formation. Chalcopyrite occurs in association with pyrite and quartz in small veinlets and numerous fractures. The deposit is immediately adjacent and parallel to a quartz-feldspar dyke and may be associated with a nearby porphyry stock. Stratigraphy, alteration and structure appear to have played an important role in ore deposition."

Jan 1, 1969

By R.P. Edwards, B.C. Flintoff

Froth flotation is one of the most widely used and effective processes for mineral benefication. First introduced in 1911, flotation technology has seen many developments over the past 80-plus years. Innovations in reagent chemistry, equipment design, process analysis and process control have given design and plant engineers a powerful set of "tools" for process optimization. However, it does not follow that all flotation systems are optimized. As Klimpel observes: "The problem with the industrial flotation process is that it is relatively easy to get reasonable results, and relatively difficult to get excellent results." Klimpel [1988] While reasonable was sufficient in the past. competitive forces will make excellent necessary in the future. Judging by the activities in many Canadian plants this transition is already underway.

Jan 1, 1995

By Chris Twigge-Molecey, John Peacey

To meet the business objectives of a metallurgical project, there is often a need for new and untried technology or equipment, whose very novelty can present serious risks to meeting those objectives. The key risk management approach is a rigorous stepwise progression from theoretical evaluations and laboratory tests to pilot plant trials. These must be followed by demonstration-scale trials before final construction of a commercial scale plant, paying particular attention to the magnitude of the scale-up between phases. Success depends on following a well-defined program, not eliminating any steps, and ensuring adequate resources are available to the development team. Chapter 6 discusses the nature of technology risks to metallurgical plant projects, and the rigorous management practices needed to identify, analyze, evaluate, and avoid or mitigate them.

Jan 1, 2015

By L. Freitag

"The Dollard oil field in southwestern Saskatchewan is a stratigraphic trap of irregular shaped perimeter. The reservoir is a low-angle monoclinal structure with a dip of approximately 100 feet in 5 miles from west to east across the long axis of the reservoir. Production of. 23° API gravity crude is obtained from a Jurassic sand referred to as the J-2-A, at an approximate depth of 4,500 feet. Reservoir studies and fluid analyses revealed that the crude is highly undersaturated, having a solution GOR of approximately 130 cubic feet of gas per barrel, that the reservoir has no definable water table, and that it appears to be of a closed-boundary type. Oil production was marked by a rapid pressure decline and it was soon evident that the greatest ultimate recovery would be best obtained if the natural driving energy of the reservoir were augmented by some artificial energy source. In support of a pressure maintenance programme, studies were conducted on flood-pot recoveries of large-diameter cores, and a potentiometric model study of the field was made. These studies indicated that a successful water flood would be obtained. The Dollard field was unitized in 1955 and pressure maintenance started in March 1956."

Jan 1, 1959

By Yves Bellemare

Entre 1983 et 1997, l'exploitation de la pierre de taille au Québec a été marquée par l'émergence et la consolidation de plusieurs nouvelles variétés de granit, provenant exclusivement ou presque de la Province de Grenville. Le Québec demeure toujours le principal expéditeur canadien de granit dimensionnel, avec des expéditions annuelles représentant près de quatre-vingt-dix pour cent des expéditions totales canadiennes de granit brut et transformé. La production annuelle de granit brut oscille, depuis 1994, autour de cent mille tonnes métriques. Cette production a plus que doublé de 63 000 à 140 000 tonnes métriques entre 1981 et 1990, mais elle a connu une chute importante en 1991 (67 000 tonnes métriques); cependant depuis 1994, elle est en forte progression (Ménard, 1998). En 1983, le granit dimensionnel était extrait de plus de vingt-cinq carrières, dont les trois quarts se localisaient dans la Province géologique de Grenville. Comparativement, en 1997, le Québec comptait trente-sept carrières actives, dont trente-cinq dans le Grenville (Gaudreau et al., 1998). Cette concentration des carrières dans la Province de Grenville s'explique par la demande accrue de nouveaux produits au fil des ans et par le potentiel élevé de découvertes de nouvelles variétés dans cette Province géologique. L'accessibilité au territoire, toujours plus grande, a facilité la mise en production de carrières favorisant la diversification des produits. Le ministère des Ressources naturelles du Québec (MRNQ) a consacré depuis 1980, beaucoup d'efforts dans la recherche de nouveaux gisements et de nouvelles variétés. En plus des programmes de subvention destinés aux prospecteurs ou aux compagnies, le ministère a réalisé des campagnes d'inventaire de pierre de taille, de pierre concassée et de pierre d'enrochement pour en connaître le potentiel géologique et à orienter les recherches futures (Nantel, 1983; Nantel et Martignole, 1991; Bellemare, 1995a, b, c, d, e, f, 1997, 1998a and b; Bellemare et Petryk, 1996a, b, c and d). Cette étude donne un aperçu des différentes variétés de pierres extraites dans la Province de Grenville entre 1983 et 1997, les situe dans leur contexte géologique et en localise les principales régions productrices. Elle est une suite à l'article publiée par Nantel (1984).

Jan 1, 2001

By W. A. Gow, J. A. Vezina

"A new process for treating scheelite for the production of tungstic tri-oxide is described. The novelty of the process resides in that an ion-ex-changer is used to convert sodium tungstate to either ammonium tung-state or tungstic acid.The process consists of a conventional hydrochloric acid leach of the scheelite concentrate, and the dissolution of the impure tungstic acid thus produced with sodium hydroxide at pH 8. The sodium tungstate solution is clarified and passed through a column of Dowex 50Wx8 ion-ex-change resin to exchange the sodium ions for either hydrogen or ammonium ions, both being suitable. The tungsten-bearing column effluent is evaporated to crystallize the tungsten as ammonium tungstate; the crystals are washed with nitric acid and water and decomposed by heat to pro-duce tungstic trioxide of high purity.Ninety-six per cent of the tungsten in the concentrate may be re-covered as tungs tic trioxide (W03), and the reagents consumed are 0.7 g HCl, 0.41 g NaOH and either 1.73 g NH.Cl or 225 g HCl per gram of tungsten."

Jan 1, 1966

By L. Lariviere, M. Grenier, R. Khalili, D. Shook

A mineral processing facility near Montreal, CEZinc, Noranda Inc., has recently implemented a leading-edge intranet solution for monitoring the performance of plant operations, and providing condition-based maintenance. This innovative multi-faceted software implementation incorporates: web-delivered plant information systems; area-wide control loop performance assessment (using sophisticated algorithms to evaluate poorly performing controllers); and integrated alarm management functions.The system has enabled a project to improve plant operations through better process control. Maintenance technicians, engineers, supervisors and managers all can see the performance of the controllers, and the performance of the plant itself, through webdelivered graphics and reports. Information is combined from many sources, real-time, historical, relational and analytical, to provide a complete picture of plant operation.The web-based solution centralizes the administration of user access, and simplifies the deployment of several different kinds of information to many desktops. It is an extensible system that allows users to create and share their own web pages and data views.The paper will discuss the solution architecture and the improvements the IT, operations, maintenance, and engineering groups have experienced, and overall benefits to the facility.

Jan 1, 2003

By J. Grant Spratt

THE Turner Valley gas-field, situated some thirty miles southwest of Calgary, Alberta, has been the topic of much discussion, particularly from a geological viewpoint. Several papers (1, 2, 3, 4, and 7) dealing with the structural and stratigraphical geology have already been published and are available for reference(l). In this article, the geological conditions will be treated only as they directly refer to the crude-oil prospects along the west flank of the anticline. HISTORY During the past twelve years, Turner Valley has been known mainly as a field which has produced a high-gravity naphtha from relatively large quantities of gas. For about ten years prior to the discovery of this naphtha-bearing gas, which is produced within the upper 450 feet of a dolomitic limestone of Carboniferous age, a minor production of light crude-oil was obtained from overlying sands of Cretaceous age. Up to June 1st of the present year, the field had produced 9,473,582 barrels of naphtha from approximately 829,000,000 M.c.f. of gas. For the past four years, the total daily production of 80 to 90 wells has averaged about 3,200 barrels of naphtha from 250,000 M.c.f. of gas. This is an average of 13 barrels per million cubic feet. The naphtha is extracted from the gas by ordinary gas-oil separators and absorption plants. After the naphtha has been recovered, about ten per cent of the gas is marketed for fuel to supply the cities of Calgary and lethbridge and intermediate cowns. The remaining ninety per cent is burned to the atmosphere, with the exception of some four to five million cubic feet per day which the Calgary Gas Company score in the depleted Bow Island gas-field.

Jan 1, 1936

By Tapio Leskinen, Jouko Koskinen, Timo Nlltti, Lappalainen Seppo, Pentti Vanninen

"The Courier 300 on-stream analysis system manufactured by Outokumpu has now been in operation at five of the company's concentration plants long enough to give a reliable basis for closer examination of the benefits achieved in control of these processes. The first system was installed at the Pyhiisalmi mine at the end of 1967. Since November 1970, two analyzers have been in operation at Pyhiisalmi feeding the assay data to a process computer which controls the whole plant and does the optimization of the process. In October 1970 the Courier 300 analysis system was installed at S. T. O. LESKINEN J. KOSKINEN the Keretti concentrator of the Outokumpu mine, followed soon by installations at the Vihanti Mine in May 1971, at the new Vuonos mine in November J 971 and at t he Kotalahti mine in December 1971. Since installation of the Courier analysis systems, considerable improvements have been achieved in the control and the economy of the plants. Immediate knowledge of the changes in the process and the possibility for rapid action has resulted in evener production and higher capacity and recovery. The recovery has been increased most significantly at the Vihanti concentrator, which operates on a complex ore. Consumption of chemicals has been reduced at all concentrators. Due to the fact that process control and partly also bilance analysis are not achieved by conventional methods any more, it has been possible to reduce the personnel of the laboratories drastically. Two of the plants, viz. the Pyhiisalmi and the Vuonos concentrators, are computercontrolled. The Vuonos concentrator started operation in January 1972 under computer control from the very beginning. The Pyhiisalmi concentrator has been computer-controlled since 1970. The Courier 300 analysis system was described in detail at the AIME Centennial Annual Meeting (1971). In this paper, less attention is paid to the analysis system. Only the sampling system of the Courier 300 is described in more detail. In the development of sampling equipment, effective use has been made of the company's wide knowledge of the problems involved and the test field offered by its concentrators. The sampling equipment includes secondary samplers and six basically different types of primary samplers, with which most sampling situations can be managed."

Jan 1, 1973

By Frank Baczek, R. Q. Honaker, D. P. Patil, B. K. Parekh

Fine refuse slurry impoundment is a requirement for the coal industry to dispose the fines. Impoundment maintenance is an on going problem for the coal industry and its breakage creates environmental as well as financial problems. Deep Cone thickener technology which has been successfully applied in the alumina industry to dewater red mud was evaluated for fine refuse slurry. Preliminary obtained in a pilot-plant test showed that properly flocculated conventional thickener underflow slurry could be thickened to about 52.5 wt % solids and could replace belt filter press. The Deep Cone thickener was also found to dewater clean coal slurry to about 70 wt % solids. Further testing of the unit at other coal preparation plant is in progress.

Jan 1, 2004

By T. W. Cavers

The Dwight-Lloyd sintering machine was the answer to the flue-dust problem of the copper blast-furnace smelter. Then came concentration by flotation, which threatened to eliminate the blast furnace from the smelting field altogether, and again the sintering process solved the problem. As is well known, the sintering process is dual in its function; it expels sulphur from the charge and it converts a powdery material into nodules or chunks that hold together. The charge is ignited on top just as it passes over the edge of the first suction box, and the oxygen of the air that is drawn downward through the charge breaks up the sulphide and oxidizes about fifty percent of the sulphur. The heat produced by this reaction in the upper stratum of the charge ignites that lying immediately below, and, when the pallett has travelled the full length of the machine, the tire has reached the graces and the fine concentrate has changed its characteristics by being partially fused and has become a more or less solid mass. When the Granby Company was smelting its ore as mined, one small D-L machine was adequate for the treatment of the flue dust, but as soon as the policy of smelting the concentrate was adopted, it became necessary to add two large machines to the sintering plant. The three sintering units, of which two are 42 in. by 396 in. and the other 42 in . by 264 in. in hearth area, have a combined capacity of from 370 to 450 tons (dry) of charge per day. The capacity varies directly as the hearth area. The sinter produced is about 88 per cent of the dry charge, or 325 to 400 tons per day. The sintered fines returned for resintering average between 30 and 35 per cent of the charge, but this is not as great a disadvantage as might appear, since the addition of hot fines improves the burning qualities of the mixture. From 50 to 54 per cent of the sulphur is eliminated in the sintering operation.

Jan 1, 1934

By E. Thomson

This type of microscopic investigation, although still in its infancy, has already found practical applications in several different phases of mining activity. The study of the transparent minerals in rocks, by means of the ordinary petrographic microscope, has for long been a very useful supplement to observations in the field, but the opaque minerals, until recently, have had to rest content with a more or less superficial determination with the hand-lens or the blow-pipe. In a great many cases, particularly where the association of metallics has been somewhat complex, this has been entirely inadequate, and the determination of these opaque minerals under the micro- scope, has opened up a new field of scientific investigation that bids fair to surpass, in practical value at least, the micro-scopic determination of the rock-forming minerals. As the details of this kind of microscopy are possibly not entirely familiar to all mining men, it might be well to outline them very briefly before dealing with the practical directions in which this method may be applied. The ordinary petro-graphic microscope, with but one extra attachment, will serve for this work. A small reflecting device, called a vertical illuminator, is inserted immediately above the objective lens. This reflects the light down to the surface of the specimen and from here the light is directed up the middle of the microscope tube to the eye. As it is desirable that the maximum amount of reflection should be secured from the surface of the section, it is first polished and set in a position perpendicular to the vertical axis of the microscope.

Jan 1, 1924

By Suzie Nantel

Crystalline igneous rocks, known commercially as granite, are exploited in Quebec f rom more than twenty-five quarries for building, ornamental and monumental purpose$. Quebec is the main Canadian producer of construction granite, accounting for nearly 90 per cent of total production. Jn the last three years, this industry has experienced an important growth due to improved marketing and use of modern equipment in rock-cutting and polishing. Jn /983 a 35 per cent sales increase is forecast. The main rock varieties extracted are the following: porphyritic pinkish grey granite and green charnockite from Riviere-dPierre, mahogany brown granite and black anorthositic rock f rom the Lac Saint-Jean area, fine-grained pink granite from Guenette, coarse-grained brown quartz monzonitefrom SaintA lexis-des-Monts. All these rock types occur in the Grenville tectonic province whereas a medium-grained, light grey granite, Devonian in age, is extensively being quarried in the southern part of the Appalachians. In the Superior province a greenish black diabase and a deep red granite are extracted. Search for new varieties and deposits is actively being carried out by prospectors and by the minis/ere de /'Energie et des Ressources du Quebec following growing demand for granitic and gabbroic rocks as dimension stone.

Jan 1, 1984

By P. H. Oliver

"The current theory of how explosives fracture rock offers no explanation for the improvements in fragmentation and the reduction of fly rock and back break which occurs when an adequate inter-row delay time is used. Nor does it explain why fragmentation improves with rectangular drill patterns where the hole spacing may be as much as four times the hole burden.A new theory of rock fragmentation is proposed which builds on the existing theory. It offers rational explanations for the many blast effects which the current theory does not address and the need for adequate timing delays between rows. It improves on the design of inter-row delay timing by defining the length of free-blasted face needed in front of a hole *Retired from Inco Ltd., Sudbury, Ontario when selecting the delay element which will provide an adequate inter-row delay time."

Jan 1, 2003

By Antonio Laguna

During the past few years, synthetic efforts have been addressed to the synthesis of polymeric materials with optical or semiconducting properties or even with capabilities to act as sensors for volatile organic compounds (1). The most recent studies have been concerned with the synthesis of heterometallic systems with short metal-metal interactions and the determination of their optical properties. These complexes are undoubtly interesting from a theoretical viewpoint and include an emerging class of luminescent materials, in which the observed luminescence results mainly from the interactions among the different metal centers, as well as the environments of these atoms. The understanding of the photophysics and photochemistry of these products could permit the design of complexes with appropriate metals and ligands chosen for individual applications. Following a synthetic strategy consisting on reactions between acid heterometal complexes and basic gold precursors we have succeded in synthesizing supramolecular assemblies formed via acid-base stacking, which display tunable luminescence or selective and reversible sensitivity to Vapour Organic Compounds (VOC?s) (2-5). In this sense, in accord with previous Mössbauer studies carried out in the gold precursor complex [AuR2]- (R = C6F5), the basic properties of this and related materials have been employed as building blocks of supramolecular assemblies in their reactions with complexes in wich the metallic centers act as lewis acids as, for instance, Tl(I) or Ag(I) (6). For instance, in the case of silver, by reacting equimolecular quantities of [NBu4][Au(C6F5)2] with AgClO4, in acetone, a solid of stoichiometry [Au2Ag2(C6F5)4(OCMe2)2]n is obtained. The polymeric nature of this material in solid state is confirmed through X-ray analyses (figure 1). It consists of polymeric chains formed by repetition of Au2Ag2 moieties linked through short gold-gold interactions. Nevertheless, in solution, the nature of this polymeric materials was still a matter of controversy and, in this case, the optical properties have been shown as useful tools in order to obtain information. Thus, while dilute acetone solutions of this complex give a emission coming from pentafluorphenyl localized ??* excited states, in accord with the presence of isolated tetranuclear Au2Ag2 units, when the measurements are done at different and higher concentrations, a band that does not obey the Lambert-Beer law appears. This deviation is consistent with molecular aggregation in solution of these units through gold-gold interactions, and a clear correlation between the emssion wavelength and the structure in the solid state and in solution is shown (figure 2). DFT calculations accord with the observed experimental behaviour and show the nature of the orbitals involved in each transition.

Oct 1, 2003