**1. Introduction**

The study of the photochemical and photophysical properties of heterocyclic compounds has received a great deal of attention during the last decade. 1,10 phenanthroline hydrate is a heterocyclic organic compound, used as a ligand in coordination chemistry; it has been the object of numerous studies, owing to its excellent complexing properties on metal ions. The multitude of applications of this cation motivated large development in synthesis of phenanthroline [1]. Various physico-chemical and biochemical techniques including UV/visible, fluorescence

and viscometric titration, thermal denaturation and differential pulse voltammetry have been employed for 1,10-phenanthroline complexes to probe the details of DNA binding [2, 3]. The influence of the presence of nitrogen atoms on the fluorescence spectral maxima of aromatic molecules is our interest, including comparison of the spectra in polar and non-polar solvents. Such studies facilitate to understand the features of chemical bonding in molecules from the topological analysis of electron densities [4] and various electrostatic properties of molecules. These fundamental properties are directly related to the properties of materials [5]. The present compound, viz. {(C12N2H8)H2O}, has been characterized with X-ray crystallography, and we are interested in fluorescence properties. The fluorescence spectra of the present compound have been obtained in various conditions. The time-dependent density functional theory (TD-DFT)/quantum theory of atoms in molecules (QTAIM)/orbital analysis and molecular electrostatic potential (MESP) theoretical calculations have been applied too.

rings are the three molecules of water. Bond lengths and valence angles compare well with the average values from related phenanthroline structures [6, 7].

*Strongly Fluorescent Heterocyclic Molecule: Crystallography, 3D Hydrogen-Bonded, Fluorescence…*

The crystal structure is built of successive rings of phenanthroline and water molecules extending parallel to (001) plane that are connected by an extensive three-dimensional hydrogen-bonded network of the type O▬H⋯O, O▬H⋯N, C▬H⋯O and C▬H⋯N (**Table 1** and **Figure 2a**). Aqua molecules and N groups are involved in hydrogen bonding and form a three-dimensional network of infinite

3(7), R<sup>2</sup>

Photoluminescence spectra were measured using a Cary Eclipse (Agilent Technologies) fluorescence spectrophotometer in a quartz cell (1.1 cm cross section) equipped with a xenon lamp and a dual monochromator. The measurements in solvents of different polarities were carried out at ambient temperature (298 K) with the slit ex/em = 20/10 nm. The photoluminescence properties of {(C12N2H8) H2O} in any solution were investigated in the visible region. The emission spectra of phh (10–<sup>4</sup> M) in non-polar solvents, viz. benzene and toluene, show maximum at 420 nm at λex = 320 nm (**Figure 3**). Studies at higher concentrations of the probe were not possible as it is marginally soluble in non-polar solvents. In polar solvents, viz. methanol, ethanol and acetonitrile, the solution exhibit emission maximum at

**D▬H⋯A D▬H H⋯A D⋯A D▬H⋯A** O1W▬H1W⋯O1Wi 0.8 (5) 2.2 (4) 2.95 (4) 163.00 O2W▬H2W⋯N1A 0.9(3) 2.1 (2) 2.92 (4) 152.00 O2W▬H2W⋯N2A 0.9(3) 2.5 (2) 3.18 (4) 135.00 O3W▬H3W⋯O3Wii 0.84(19) 2.1 (2) 2.96 (4) 174.00 O1W▬H11W⋯N1B 1.10(19) 1.9 (2) 2.90 (3) 152.00 O1W▬H11W⋯N2B 1.10(19) 2.4 (3) 3.18 (3) 125.00 O2W▬H22W⋯O2Wiii 0.8(2) 2.1 (2) 2.94 (3) 169.00 O3W▬H33W⋯N1C 0.86(18) 2.5 (2) 3.16 (3) 138.00 O3W▬H33W⋯N2C 0.86(18) 2.2 (2) 2.97 (3) 148.00 C1B▬H1B⋯O1Wi 0.9300 2.5900 3.44 (5) 152.00 C3A▬H3A⋯N1Civ 0.9300 2.4900 3.28 (5) 142.00 C8C▬H037⋯N2Bv 0.9200 2.4700 3.31 (5) 151.00 C5B▬H5B⋯N2A 0.9300 2.5700 3.41 (5) 151.00 C8B▬H8B⋯N2Avi 0.9300 2.5000 3.25 (5) 139.00 Symmetry codes: (i) y + 1, x y + 1, z + 1/3; (ii) x + y + 1, x + 1, z 1/3; (iii) y, x y, z + 1/3;

(iv) x + y + 1, x + 1, z + 2/3; (v) x + y, x, z 1/3; (vi) y, x y, z 2/3.

**Table 1.**

**79**

*Hydrogen bond geometry (Å, °).*

which deploy along the two crystallographic axes a and b (**Figure 2b** and **c**) [8].

1(5), R2

2(9), R5

6(22) and R4

6(15)]

**3. Supramolecular features**

**4. Luminescent properties**

chains and variable degrees of rings [C3

*DOI: http://dx.doi.org/10.5772/intechopen.90271*
