The current discovery and derivatization of borane family members suggest that boron chemistry is about to begin a growth trajectory resembling that of carbon chemistry. A number of studies have been done previously on the use of boron clusters in pharmaceuticals such as anti-biotics, anti-inflammatory medications, cancer therapy, boron neutron capture therapy, crystal engineering, etc., [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36]]. The anisotropic distribution of electrons in these boron clusters led to the formation of stable non-covalent complexes with organic molecules [37,38]. Modern chemistry, including the design of materials and molecular biology, have relied heavily on non-covalent interactions [[39], [40], [41], [42], [43]]. The de-boronation of closo-boranes resulted in the nido species, which showed the stability of the parental closo-boranes [44]. The binding capability of the B–H component in boron cluster molecules was crucial to medicinal chemistry [19,43]. The hydridic character of the B–H bond allowed boron cluster to engage with proton donors in protein receptor sites in a way that differed from the hydrogen bonding and hydrophobic interactions that were typical of organic molecules, according to X-ray studies and molecular dynamic simulations [43,45]. The doping of the carbon atoms in boron clusters were resulted in an increase in the nature of the hydridic character of the B–H bond because of the higher electronegativity of carbon atom [46]. In this connection, many computational studies were reported [37,38,47]. In one of the notable studies, the closo-carboranes’ (BH)2--vertices were systematically replaced by heteroatoms like S2+, Se2+ and CH+ without disturbing the overall charge and their interaction with organic molecules like benzene (BEN), trimethylamine (TMA), dimethyl ether, acetone and formamide were reported [37,38]. Following the study, we focused our attention on nido-carboboranes. Nido-boranes (B11H11)4-, having one vertex less than closo-boranes, are inorganic compounds with unique properties. Halogenated nido-carboranes are expected to acquire unique properties that complement their binding capabilities. These have an open pentagonal face and are similar to the closo-analogues (BH)2-, and their vertices can be replaced with heteroatom-based moieties, viz., (CH)-, S, NH- and P [48]. These replacements distorted the open pentagonal ring. Therefore, it would be interesting to study their stability as a structure and binding their capabilities. Within the nido-borane clusters, the 11-vertex systems have the maximum number of known examples. F.A. Kiani et al., applying density functional theory, studied the structure and relative stability of 11-vertex nido-boranes and carboranes [48]. Recently, P. Melichar et al., examined the nature of the bonding in heteroborane clusters using a quantum chemical tool, the intrinsic atomic/bond orbital approach. They reported that the bonding in the heteroatom is multi-centered in nature [46]. D. Tu et al., studied the non-covalent interaction between the nido-cage--π bond experimentally and through theoretical study, they predicted that the binding nature was similar to those found in cyclopentadienyl anion--π or π—π interaction [39]. These types of interactions between macromolecules and nido-heteroboranes enhanced the durability and biological activity of the boron cluster system [21]. The presence of halogen atoms further augmented the binding capabilities of these kinds of non-covalent interactions [[40], [41], [42], [43],49]. In this work, we considered the following experimentally known nido-carboranes where one or more (BH)2- species were replaced by isoelectronic (CH)- species. They're: nido-7-CB10H12, nido-7,8-C2B9H11, nido-7,8,9-C3B8H10 and nido-7,8,9,10-C4B7H9. It was reported that the Br atom bonded to the carbon atom has a higher Vs,max value than the Br-bonded boron atom [37,38]. Therefore, in the present study, we've decided to replace the terminal (exo) hydrogen bonded to one of the carbon atoms by the Br atom and –OH group, and examine their interacting abilities with BEN and TMA. The reason for choosing the Br atom was that, among the halogens, it is a synthetically feasible and medium-sized atom with bipolar characteristics, i.e., it has the ability to interact with both the negative and positive sites of the receptor. This multidimensional binding ability of Br makes it a unique character. On the other hand, –OH is unidirectional but known to possess stronger binding capabilities due to its high ESP. Through our study, we expect that if the binding capacity of the Br excel at least half the ability of –OH, then its values towards applicability would be enormous.

In the following section, we present the computational details. In the next section, we discuss the results on electrostatic potential, structures and stabilities of the complexes and finally we conclude.