Carbon fullerenes allotropic forms

If you re a sports fan, you ve almost certainly seen this structure before. It is that of a soccer ball with a carbon atom at each vertex. Smalley and his colleagues could have named this allotropic form of carbon "carbosoccer" or "soc-cerene," but they didn t. Instead they called it "buckminster fullerene" after the architect R. Buckminster Fuller, whose geodesic domes vaguely resembled truncated soccer balls. 

The state of research on the two classes of acetylenic compounds described in this article, the cyclo[ ]carbons and tetraethynylethene derivatives, differs drastically. The synthesis of bulk quantities of a cyclocarbon remains a fascinating challenge in view of the expected instability of these compounds. These compounds would represent a fourth allotropic form of carbon, in addition to diamond, graphite, and the fullerenes. The full spectral characterization of macroscopic quantities of cyclo-C should provide a unique experimental calibration for the power of theoretical predictions dealing with the electronic and structural properties of conjugated n-chromophores of substantial size and number of heavy atoms. We believe that access to bulk cyclocarbon quantities will eventually be accomplished by controlled thermal or photochemical cycloreversion reactions of structurally defined, stable precursor molecules similar to those described in this review. 

The Nobel prize in Chemistry for the year 1996 was awarded for the discovery of the fullerenes, the third allotropic form of carbon, with Cgo and C70 as the two most prominent representatives. While the fullerenes of course are the epitome of carbon-rich molecular compounds, it is an irony that their synthesis is more of a physical phase transition, taking place under drastic conditions [1]. 

Fullerenes, the third allotropic form of carbon along with graphite and diamond, are a novel class of spheroidally shaped molecules made exclusively of carbon atoms. They have generated much enthusiasm and numerous research efforts during the past few years.206 Hence, the chemical and physical features of C6o, also named... 

In 1985, another allotropic form of carbon, fullerenes, were discovered. Two important fullerenes are C60 and C70. 

V.I. Sokolov, I.V. Stankevich. Fullerenes - new allotropic forms of carbon structure, electron structure and chemical properties. // Success in chemistry, 1993, v.62, N°5, p.455-473. 

The toxicity of this third allotropic form of carbon is an aspect related to application in medicine and biology, while the concern about the environmental impact is due to the industrial production of fullerenes. Many studies are dedicated to both aspects and, so far, it is not possible to have a definitive answer although the current findings allow some optimistic vision. 

The emerging field of nanotechnology is affirming its increasing importance day by day. In this context fullerenes and carbon nano tubes (CNTs) play an important role. These new allotropic forms of carbon have been discovered in the last two decades, and, since then, they have stimulated the curiosity and interest of physicists and chemists. 

Carbon is unique among chemical elements since it exists in different forms and microtextures transforming it into a very attractive material that is widely used in a broad range of electrochemical applications. Carbon exists in various allotropic forms due to its valency, with the most well-known being carbon black, diamond, fullerenes, graphene and carbon nanotubes. This review is divided into four sections. In the first two sections the structure, electronic and electrochemical properties of carbon are presented along with their applications. The last two sections deal with the use of carbon in polymer electrolyte fuel cells (PEFCs) as catalyst support and oxygen reduction reaction (ORR) electrocatalyst. 

No other allotropic forms of carbon were known until ten years ago then arising from studies of interstellar carbonaceous molecules, a new form of carbon, namely fullerene or buckyballs , was discovered (Kroto et al 1985), for which the authors received the 1996 Nobel Prize for Chemistry. Its structure is basically a ball or spherically shaped cage consisting of pure carbon. The most stable... 

With the exception of the gaseous low-carbon molecules Ci,C2, C3,C4,C5,.. the carbon element exists in the diamond, graphite, fullerene, and amorphous allotropic forms. 

Since the discovery of fullerenes the scientific community has been taking an active interest in peculiarities of the fullerene formation and structure, physical and chemical properties. The fourth allotropic modification of carbon (fullerene) is unique molecule having a spatial structure with icosahedral symmetry and showing distinctive properties in interaction with other substances. Under certain conditions fullerenes can accept and donate hydrogen atoms to form hydrofullerenes. 

Different forms of an element with different properties. For example, diamond, graphite, and fullerenes are different allotropic forms of elemental carbon, (p. 737)... 

Fullerenes were first identified by Smalley and coworkers in 1985. Although a later section in this chapter will be devoted to this topic, it is briefly mentioned here because C60 is an allotropic form of carbon. The structure of this form of carbon is shown in Figure 10.4. 

In the mid-1980s, virtually simultaneous reports on two new precise molecular level constructions of sub-nanoscopic/nanoscopic size appeared in the literature. In 1984 we (DAT) reported the synthesis, isolation and characterization of the first iterated series of Starburst/cascade dendrimers based on genealogical synthesis [2, 77-83]. The following year Smalley, Curl and Kroto described the first observation of a 60-carbon fullerene by mass spectroscopy [43a]. More recently the synthesis of buckminsterfullerene has been achieved by physicists at the Max Planck Institute in Heidelberg [44] to give macroscopic quantities of the third allotropic and first molecular form of carbon, named after Buckminster Fuller. Similarities between these two constructions were not initially apparent, but in retrospect they deserve comment in so far as they each involve molecular level synthesis leading to closed geometrical architecture". 

Sokolov V.I., Stankevich I.V. Fullerenes and new allotropic forms of carbon ... 

We used to believe that there are three allotropic forms of carbon graphite, diamond, and amorphous carbon. However, an important new carbon al-lotrope, the fullerenes, was discovered as recently as the 1980s. The most famous fullerene is buckminsterfullerene, Ceo, which is depicted in Fig. 3.1. The structure of this soccer ball-shaped molecule consists of a sphere of sixty carbon atoms arranged in pentagons and hexagons each carbon pentagon is surrounded by five carbon hexagons. 

Carbon is the basis of all life on earth, and without a doubt, one of the most versatile elements known to man. More than ten million carbon compounds are known today, many times more than that of any other element. Carbon itself exists in several allotropes. Its flexible electron configuration allows carbon to form three hybridization states which lead to different types of covalent bonding. The most representative macroscopic forms of carbon are graphite and diamond. In 1985, Kroto et al. discovered a third carbon allotrope, the fullerenes. While their experiments aimed at understanding the mechanisms by which long chained carbon molecules are formed in interstellar space, their results opened a new era in science - the beginning of nanotechnology. 

The fullerenes, which contain only carbon, are an allotropic form of carbon discovered in 1985. All the fullerenes have even numbers of atoms, with formulas ranging up to C400 and higher. Their tt bonds are conjugated tr electron systems. 

The combination of sp , sp and sp hybridized atoms can give rise to a large number of carbon allotropic forms and phases, but only carbon solids based on all sp (diamond) and sp (graphite, fullerene) hybridization are well known and characterized [1]. In addition there are innumerable transitional forms of carbon where sp and sp hybridization bonds co-exist in the same... 

In this chapter we consider the analysis of the spectra from non-hydrogenous materials ( 11.1) with chlorine ( 11.1.1) and some minerals ( 11.1.2) as examples. Carbon ( 11.2) in its allotropic forms of diamond ( 11.2.1), graphite ( 11.2.2) and the fullerenes and their derivatives ( 11.2.3) has been studied extensively by INS spectroscopy. 

Why are there so many organic compounds There are several reasons. First, carbon can form stable, covalent bonds with other carbon atoms. Consider three of the allotropic forms of elemental carbon graphite, diamond, and buckminster-fullerene. Models of these allotropes are shown in Figure 11.1. 

Carbon materials have particular characteristics due to differences in chemical bond formation. Allotropic forms of carbon that have been discovered can be categorized into five types from the standpoint of the type of hybridization of the valence orbitals (1) -hybridization (2) -hybridization (3) -hybridization (4) mixed hybridization (sp3 + sp2) and (5) a valance state characterized by a fractional degree of hybridization (spm, where 1 diamond-like carbon, and fullerenes correspond to groups (1), (3), (4), and (5), respectively. 

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