You’ve most likely heard of bioluminescence and marine creatures that produce light as a result of specific chemical reactions in living organisms. For some reason, people often confuse bioluminescence with fluorescence and vice versa. In fact, fluorescence is a totally different phenomenon that occurs when light is emitted by certain materials.
As you may have seen before, glass tubes containing gasses create different colors. For example, argon glows blue, helium produces pink light, and neon glows red-orange. Similarly, certain organic compounds give off visible light after they absorb light or electromagnetic radiation. But which compound is most fluorescent in organic chemistry? Here’s the answer for you.
What Is Fluorescence in Chemistry?
Before we discuss organic compounds that fluoresce, let’s explain what fluorescence in chemistry is to better understand the concept of molecules shining and glowing brightly.
Fluorescence is a physico-chemical process during which a molecule absorbs shorter-wavelength photons and re-emits them as longer-wavelength photons, producing visible light.
So, fluorescence is a two-stage process. The first stage is also referred to as excitation, during which short-wavelength high-energy photons are absorbed. The second stage of fluorescence is known as emission, during which some of the absorbed photons are released as long-wavelength low-energy photons.
Read more about fluorescence in this scientific review article.
What Is the Most Fluorescent Organic Compound?
While we can characterize different compounds based on their size, structure, and properties, we can’t really tell which compound is most fluorescent in organic chemistry.
There is no specific organic compound that can be identified as the most fluorescent molecule in organic chemistry. Many organic compounds can fluoresce when being electrically excited and then relaxed to the ground state.
So, although there are many fluorescent organic compounds, it’s pretty much impossible to determine which one is the most fluorescent. This is because it all depends on the specific conditions, such as the frequencies of excitation and emission. Besides, the major variables that affect fluorescence are molecular structure and the chemical environment.
Factors that Affect Fluorescence
As a matter of fact, fluorescence can be affected by a few different variables.
The main factors that affect the fluorescence of organic compounds include molecular structure, structural rigidity, temperature, and pH.
Here are the factors that affect how fluorescent organic compounds are.
Molecular Structure
In terms of the structure of organic compounds and fluorescence, the compounds containing an aromatic group with low-energy π→π∗ transitions tend to be the most fluorescent. These transitions refer to an electron moving from a bonding π orbital to an antibonding π∗ orbital.
When it comes to nitrogen heterocyclics, simple heterocyclics (such as pyridine) have not been observed to exhibit fluorescence. On the other hand, fused-ring structures of nitrogen heterocyclics (such as quinoline) do fluoresce.
Structural Rigidity
Another factor that contributes to the fluorescence of organic compounds is their structural rigidity. Organic compounds with rigid structures fluoresce. This can also be explained by the fact that quantum efficiency in rigid molecules is higher than in unrigid compounds.
Temperature
While the structure and characteristics of molecules affect fluorescence, specific conditions of the experiment can also have a significant impact. For example, if the temperature is increased, the quantum efficiency is decreased, making the compound less fluorescent.
pH of a Solution
Besides, fluorescence also decreases if a given solvent contains heavy atoms. In addition, the fluorescence of some organic compounds that produce protonated and unprotonated molecules is also pH-dependent. This chapter on Chem LibreTexts provides further details about the fluorescence of organic compounds and the factors that affect fluorescence.
What Are the Uses of Fluorescent Organic Compounds?
Fluorescence, in general, has plenty of practical uses and applications in different industries. In the case of organic compounds that fluoresce, they are widely used in medical microbiology.
Fluorescent organic compounds are often used as biological detectors and fluorescent labels. Fluorescence is also used for quantitative and qualitative analysis. Besides, fluorescent organic compounds are used in spectroscopy as diagnostic and research tools in medical sciences.
When it comes to biological studies, fluorescence is considered to be one of the essential analytical methods. Therefore, certain organic compounds are often used as fluorescent sensors for biological applications.
In addition, organic compounds that fluoresce are also used as fluorescent dyes that bind to specific functional groups to visualize biomolecules during the process called fluorescent labeling.
Besides, fluorescence spectroscopy is widely used for the discovery and analysis of bloodstains at crime scenes. Fluorescence allows professionals to explore the endogenous fluorophores within bloodstains, providing crucial information to the investigation.
According to this review paper, fluorescence spectroscopy is a potential diagnostic tool that may be used as a routine diagnostic tool for microorganisms in the future. Along with being affordable, rapid, and sensitive, fluorescence has a potential to become an excellent diagnostic tool.
Common Fluorescent Compounds in Organic Chemistry
Let’s discuss a few organic compounds that show fluorescent characteristics.
Organic compounds that fluoresce are fluorophore, fluoranthene, coronene, pyrene, perylene, BODIPY, coumarin, quinoline, and carbazole.
While there are many different organic compounds that are characterized by fluorescence, these are some of the most commonly used fluorescent organic compounds.
When choosing between these fluorescent compounds, one should consider a few factors. These include the desired application of a compound and specific properties, such as excitation and emission wavelengths, molecular structure, structural rigidity, quantum yield, and solubility.
